/*
 
* Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
 
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 
*
 
* This code is free software; you can redistribute it and/or modify it
 
* under the terms of the GNU General Public License version 2 only, as
 
* published by the Free Software Foundation.
  
Oracle designates this
 
* particular file as subject to the "Classpath" exception as provided
 
* by Oracle in the LICENSE file that accompanied this code.
 
*
 
* This code is distributed in the hope that it will be useful, but WITHOUT
 
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 
* FITNESS FOR A PARTICULAR PURPOSE.
  
See the GNU General Public License
 
* version 2 for more details (a copy is included in the LICENSE file that
 
* accompanied this code).
 
*
 
* You should have received a copy of the GNU General Public License version
 
* 2 along with this work; if not, write to the Free Software Foundation,
 
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 
*
 
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 
* or visit www.oracle.com if you need additional information or have any
 
* questions.
 
*/

package java.util;
import java.io.Serializable;
import java.io.ObjectOutputStream;
import java.io.IOException;
import java.lang.reflect.Array;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.UnaryOperator;
import java.util.stream.IntStream;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

/**
 
* This class consists exclusively of static methods that operate on or return
 
* collections.
  
It contains polymorphic algorithms that operate on
 
* collections, "wrappers", which return a new collection backed by a
 
* specified collection, and a few other odds and ends.
 
*
 
* <p>The methods of this class all throw a <tt>NullPointerException</tt>
 
* if the collections or class objects provided to them are null.
 
*
 
* <p>The documentation for the polymorphic algorithms contained in this class
 
* generally includes a brief description of the <i>implementation</i>.
  
Such
 
* descriptions should be regarded as <i>implementation notes</i>, rather than
 
* parts of the <i>specification</i>.
  
Implementors should feel free to
 
* substitute other algorithms, so long as the specification itself is adhered
 
* to.
  
(For example, the algorithm used by <tt>sort</tt> does not have to be
 
* a mergesort, but it does have to be <i>stable</i>.)
 
*
 
* <p>The "destructive" algorithms contained in this class, that is, the
 
* algorithms that modify the collection on which they operate, are specified
 
* to throw <tt>UnsupportedOperationException</tt> if the collection does not
 
* support the appropriate mutation primitive(s), such as the <tt>set</tt>
 
* method.
  
These algorithms may, but are not required to, throw this
 
* exception if an invocation would have no effect on the collection.
  
For
 
* example, invoking the <tt>sort</tt> method on an unmodifiable list that is
 
* already sorted may or may not throw <tt>UnsupportedOperationException</tt>.
 
*
 
* <p>This class is a member of the
 
* <a href="{@docRoot}/../technotes/guides/collections/index.html">
 
* Java Collections Framework</a>.
 
*
 
* @author
  
Josh Bloch
 
* @author
  
Neal Gafter
 
* @see
     
Collection
 
* @see
     
Set
 
* @see
     
List
 
* @see
     
Map
 
* @since
   
1.2
 
*/


public class Collections {
    
// Suppresses default constructor, ensuring non-instantiability.
    
private Collections() {
    
}

    
// Algorithms

    
/*
     
* Tuning parameters for algorithms - Many of the List algorithms have
     
* two implementations, one of which is appropriate for RandomAccess
     
* lists, the other for "sequential."
  
Often, the random access variant
     
* yields better performance on small sequential access lists.
  
The
     
* tuning parameters below determine the cutoff point for what constitutes
     
* a "small" sequential access list for each algorithm.
  
The values below
     
* were empirically determined to work well for LinkedList. Hopefully
     
* they should be reasonable for other sequential access List
     
* implementations.
  
Those doing performance work on this code would
     
* do well to validate the values of these parameters from time to time.
     
* (The first word of each tuning parameter name is the algorithm to which
     
* it applies.)
     
*/

    
private static final int BINARYSEARCH_THRESHOLD
   
= 5000;
    
private static final int REVERSE_THRESHOLD
        
=
   
18;
    
private static final int SHUFFLE_THRESHOLD
        
=
    
5;
    
private static final int FILL_THRESHOLD
           
=
   
25;
    
private static final int ROTATE_THRESHOLD
         
=
  
100;
    
private static final int COPY_THRESHOLD
           
=
   
10;
    
private static final int REPLACEALL_THRESHOLD
     
=
   
11;
    
private static final int INDEXOFSUBLIST_THRESHOLD =
   
35;

    
/**
     
* Sorts the specified list into ascending order, according to the
     
* {@linkplain Comparable natural ordering} of its elements.
     
* All elements in the list must implement the {@link Comparable}
     
* interface.
  
Furthermore, all elements in the list must be
     
* <i>mutually comparable</i> (that is, {@code e1.compareTo(e2)}
     
* must not throw a {@code ClassCastException} for any elements
     
* {@code e1} and {@code e2} in the list).
     
*
     
* <p>This sort is guaranteed to be <i>stable</i>:
  
equal elements will
     
* not be reordered as a result of the sort.
     
*
     
* <p>The specified list must be modifiable, but need not be resizable.
     
*
     
* @implNote
     
* This implementation defers to the {@link List#sort(Comparator)}
     
* method using the specified list and a {@code null} comparator.
     
*
     
* @param
  
<T> the class of the objects in the list
     
* @param
  
list the list to be sorted.
     
* @throws ClassCastException if the list contains elements that are not
     
*
         
<i>mutually comparable</i> (for example, strings and integers).
     
* @throws UnsupportedOperationException if the specified list's
     
*
         
list-iterator does not support the {@code set} operation.
     
* @throws IllegalArgumentException (optional) if the implementation
     
*
         
detects that the natural ordering of the list elements is
     
*
         
found to violate the {@link Comparable} contract
     
* @see List#sort(Comparator)
     
*/

    
@SuppressWarnings("unchecked")
    
public static <T extends Comparable<? super T>> void sort(List<T> list) {
        
list.sort(null);
    
}

    
/**
     
* Sorts the specified list according to the order induced by the
     
* specified comparator.
  
All elements in the list must be <i>mutually
     
* comparable</i> using the specified comparator (that is,
     
* {@code c.compare(e1, e2)} must not throw a {@code ClassCastException}
     
* for any elements {@code e1} and {@code e2} in the list).
     
*
     
* <p>This sort is guaranteed to be <i>stable</i>:
  
equal elements will
     
* not be reordered as a result of the sort.
     
*
     
* <p>The specified list must be modifiable, but need not be resizable.
     
*
     
* @implNote
     
* This implementation defers to the {@link List#sort(Comparator)}
     
* method using the specified list and comparator.
     
*
     
* @param
  
<T> the class of the objects in the list
     
* @param
  
list the list to be sorted.
     
* @param
  
c the comparator to determine the order of the list.A
     
*
        
{@code null} value indicates that the elements' <i>natural
     
*
        
ordering</i> should be used.
     
* @throws ClassCastException if the list contains elements that are not
     
*
         
<i>mutually comparable</i> using the specified comparator.
     
* @throws UnsupportedOperationException if the specified list's
     
*
         
list-iterator does not support the {@code set} operation.
     
* @throws IllegalArgumentException (optional) if the comparator is
     
*
         
found to violate the {@link Comparator} contract
     
* @see List#sort(Comparator)
     
*/

    
@SuppressWarnings({"unchecked", "rawtypes"})
    
public static <T> void sort(List<T> list, Comparator<? super T> c) {
        
list.sort(c);
    
}


    
/**
     
* Searches the specified list for the specified object using the binary
     
* search algorithm.
  
The list must be sorted into ascending order
     
* according to the {@linkplain Comparable natural ordering} of its
     
* elements (as by the {@link #sort(List)} method) prior to making this
     
* call.
  
If it is not sorted, the results are undefined.If the list
     
* contains multiple elements equal to the specified object, there is no
     
* guarantee which one will be found.
     
*
     
* <p>This method runs in log(n) time for a "random access" list (which
     
* provides near-constant-time positional access).
  
If the specified list
     
* does not implement the {@link RandomAccess} interface and is large,
     
* this method will do an iterator-based binary search that performs
     
* O(n) link traversals and O(log n) element comparisons.
     
*
     
* @param
  
<T> the class of the objects in the list
     
* @param
  
list the list to be searched.
     
* @param
  
key the key to be searched for.
     
* @return the index of the search key, if it is contained in the list;
     
*
         
otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>.
  
The
     
*
         
<i>insertion point</i> is defined as the point at which the
     
*
         
key would be inserted into the list: the index of the first
     
*
         
element greater than the key, or <tt>list.size()</tt> if all
     
*
         
elements in the list are less than the specified key.
  
Note
     
*
         
that this guarantees that the return value will be &gt;= 0 if
     
*
         
and only if the key is found.
     
* @throws ClassCastException if the list contains elements that are not
     
*
         
<i>mutually comparable</i> (for example, strings and
     
*
         
integers), or the search key is not mutually comparable
     
*
         
with the elements of the list.
     
*/

    
public static <T>
    
int binarySearch(List<? extends Comparable<? super T>> list, T key) {
        
if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD)
            
return Collections.indexedBinarySearch(list, key);
        
else
            
return
Collections.iteratorBinarySearch(list, key);
    
}

    
private static <T>
    
int indexedBinarySearch(List<? extends Comparable<? super T>> list, T key) {
        
int low = 0;
        
int high = list.size()-1;

        
while (low <= high) {
            
int mid = (low + high) >>> 1;
            
Comparable<? super T> midVal = list.get(mid);
            
int cmp = midVal.compareTo(key);

            
if (cmp < 0)
                
low = mid + 1;
            
else if (cmp > 0)
                
high = mid - 1;
            
else
                
return
mid; // key found
        
}
        
return -(low + 1);
  
// key not found
    
}

    
private static <T>
    
int iteratorBinarySearch(List<? extends Comparable<? super T>> list, T key)
    
{
        
int low = 0;
        
int high = list.size()-1;
        
ListIterator<? extends Comparable<? super T>> i = list.listIterator();

        
while (low <= high) {
            
int mid = (low + high) >>> 1;
            
Comparable<? super T> midVal = get(i, mid);
            
int cmp = midVal.compareTo(key);

            
if (cmp < 0)
                
low = mid + 1;
            
else if (cmp > 0)
                
high = mid - 1;
            
else
                
return
mid; // key found
        
}
        
return -(low + 1);
  
// key not found
    
}

    
/**
     
* Gets the ith element from the given list by repositioning the specified
     
* list listIterator.
     
*/

    
private static <T> T get(ListIterator<? extends T> i, int index) {
        
T obj = null;
        
int pos = i.nextIndex();
        
if (pos <= index) {
            
do {
                
obj = i.next();
            
} while (pos++ < index);
        
} else {
            
do {
                
obj = i.previous();
            
} while (--pos > index);
        
}
        
return obj;
    
}

    
/**
     
* Searches the specified list for the specified object using the binary
     
* search algorithm.
  
The list must be sorted into ascending order
     
* according to the specified comparator (as by the
     
* {@link #sort(List, Comparator) sort(List, Comparator)}
     
* method), prior to making this call.
  
If it is
     
* not sorted, the results are undefined.
  
If the list contains multiple
     
* elements equal to the specified object, there is no guarantee which one
     
* will be found.
     
*
     
* <p>This method runs in log(n) time for a "random access" list (which
     
* provides near-constant-time positional access).
  
If the specified list
     
* does not implement the {@link RandomAccess} interface and is large,
     
* this method will do an iterator-based binary search that performs
     
* O(n) link traversals and O(log n) element comparisons.
     
*
     
* @param
  
<T> the class of the objects in the list
     
* @param
  
list the list to be searched.
     
* @param
  
key the key to be searched for.
     
* @param
  
c the comparator by which the list is ordered.
     
*
         
A <tt>null</tt> value indicates that the elements'
     
*
         
{@linkplain Comparable natural ordering} should be used.
     
* @return the index of the search key, if it is contained in the list;
     
*
         
otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>.
  
The
     
*
         
<i>insertion point</i> is defined as the point at which the
     
*
         
key would be inserted into the list: the index of the first
     
*
         
element greater than the key, or <tt>list.size()</tt> if all
     
*
         
elements in the list are less than the specified key.
  
Note
     
*
         
that this guarantees that the return value will be &gt;= 0 if
     
*
         
and only if the key is found.
     
* @throws ClassCastException if the list contains elements that are not
     
*
         
<i>mutually comparable</i> using the specified comparator,
     
*
         
or the search key is not mutually comparable with the
     
*
         
elements of the list using this comparator.
     
*/

    
@SuppressWarnings("unchecked")
    
public static <T> int binarySearch(List<? extends T> list, T key, Comparator<? super T> c) {
        
if (c==null)
            
return binarySearch((List<? extends Comparable<? super T>>) list, key);

        
if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD)
            
return Collections.indexedBinarySearch(list, key, c);
        
else
            
return
Collections.iteratorBinarySearch(list, key, c);
    
}

    
private static <T> int indexedBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) {
        
int low = 0;
        
int high = l.size()-1;

        
while (low <= high) {
            
int mid = (low + high) >>> 1;
            
T midVal = l.get(mid);
            
int cmp = c.compare(midVal, key);

            
if (cmp < 0)
                
low = mid + 1;
            
else if (cmp > 0)
                
high = mid - 1;
            
else
                
return
mid; // key found
        
}
        
return -(low + 1);
  
// key not found
    
}

    
private static <T> int iteratorBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) {
        
int low = 0;
        
int high = l.size()-1;
        
ListIterator<? extends T> i = l.listIterator();

        
while (low <= high) {
            
int mid = (low + high) >>> 1;
            
T midVal = get(i, mid);
            
int cmp = c.compare(midVal, key);

            
if (cmp < 0)
                
low = mid + 1;
            
else if (cmp > 0)
                
high = mid - 1;
            
else
                
return
mid; // key found
        
}
        
return -(low + 1);
  
// key not found
    
}

    
/**
     
* Reverses the order of the elements in the specified list.<p>
     
*
     
* This method runs in linear time.
     
*
     
* @param
  
list the list whose elements are to be reversed.
     
* @throws UnsupportedOperationException if the specified list or
     
*
         
its list-iterator does not support the <tt>set</tt> operation.
     
*/

    
@SuppressWarnings({"rawtypes", "unchecked"})
    
public static void reverse(List<?> list) {
        
int size = list.size();
        
if (size < REVERSE_THRESHOLD || list instanceof RandomAccess) {
            
for (int i=0, mid=size>>1, j=size-1; i<mid; i++, j--)
                
swap(list, i, j);
        
} else {
            
// instead of using a raw type here, it's possible to capture
            
// the wildcard but it will require a call to a supplementary
            
// private method
            
ListIterator fwd = list.listIterator();
            
ListIterator rev = list.listIterator(size);
            
for (int i=0, mid=list.size()>>1; i<mid; i++) {
                
Object tmp = fwd.next();
                
fwd.set(rev.previous());
                
rev.set(tmp);
            
}
        
}
    
}

    
/**
     
* Randomly permutes the specified list using a default source of
     
* randomness.
  
All permutations occur with approximately equal
     
* likelihood.
     
*
     
* <p>The hedge "approximately" is used in the foregoing description because
     
* default source of randomness is only approximately an unbiased source
     
* of independently chosen bits. If it were a perfect source of randomly
     
* chosen bits, then the algorithm would choose permutations with perfect
     
* uniformity.
     
*
     
* <p>This implementation traverses the list backwards, from the last
     
* element up to the second, repeatedly swapping a randomly selected element
     
* into the "current position".
  
Elements are randomly selected from the
     
* portion of the list that runs from the first element to the current
     
* position, inclusive.
     
*
     
* <p>This method runs in linear time.
  
If the specified list does not
     
* implement the {@link RandomAccess} interface and is large, this
     
* implementation dumps the specified list into an array before shuffling
     
* it, and dumps the shuffled array back into the list.
  
This avoids the
     
* quadratic behavior that would result from shuffling a "sequential
     
* access" list in place.
     
*
     
* @param
  
list the list to be shuffled.
     
* @throws UnsupportedOperationException if the specified list or
     
*
         
its list-iterator does not support the <tt>set</tt> operation.
     
*/

    
public static void shuffle(List<?> list) {
        
Random rnd = r;
        
if (rnd == null)
            
r = rnd = new Random(); // harmless race.
        
shuffle(list, rnd);
    
}

    
private static Random r;

    
/**
     
* Randomly permute the specified list using the specified source of
     
* randomness.
  
All permutations occur with equal likelihood
     
* assuming that the source of randomness is fair.<p>
     
*
     
* This implementation traverses the list backwards, from the last element
     
* up to the second, repeatedly swapping a randomly selected element into
     
* the "current position".
  
Elements are randomly selected from the
     
* portion of the list that runs from the first element to the current
     
* position, inclusive.<p>
     
*
     
* This method runs in linear time.
  
If the specified list does not
     
* implement the {@link RandomAccess} interface and is large, this
     
* implementation dumps the specified list into an array before shuffling
     
* it, and dumps the shuffled array back into the list.
  
This avoids the
     
* quadratic behavior that would result from shuffling a "sequential
     
* access" list in place.
     
*
     
* @param
  
list the list to be shuffled.
     
* @param
  
rnd the source of randomness to use to shuffle the list.
     
* @throws UnsupportedOperationException if the specified list or its
     
*
         
list-iterator does not support the <tt>set</tt> operation.
     
*/

    
@SuppressWarnings({"rawtypes", "unchecked"})
    
public static void shuffle(List<?> list, Random rnd) {
        
int size = list.size();
        
if (size < SHUFFLE_THRESHOLD || list instanceof RandomAccess) {
            
for (int i=size; i>1; i--)
                
swap(list, i-1, rnd.nextInt(i));
        
} else {
            
Object arr[] = list.toArray();

            
// Shuffle array
            
for (int i=size; i>1; i--)
                
swap(arr, i-1, rnd.nextInt(i));

            
// Dump array back into list
            
// instead of using a raw type here, it's possible to capture
            
// the wildcard but it will require a call to a supplementary
            
// private method
            
ListIterator it = list.listIterator();
            
for (int i=0; i<arr.length; i++) {
                
it.next();
                
it.set(arr[i]);
            
}
        
}
    
}

    
/**
     
* Swaps the elements at the specified positions in the specified list.
     
* (If the specified positions are equal, invoking this method leaves
     
* the list unchanged.)
     
*
     
* @param list The list in which to swap elements.
     
* @param i the index of one element to be swapped.
     
* @param j the index of the other element to be swapped.
     
* @throws IndexOutOfBoundsException if either <tt>i</tt> or <tt>j</tt>
     
*
         
is out of range (i &lt; 0 || i &gt;= list.size()
     
*
         
|| j &lt; 0 || j &gt;= list.size()).
     
* @since 1.4
     
*/

    
@SuppressWarnings({"rawtypes", "unchecked"})
    
public static void swap(List<?> list, int i, int j) {
        
// instead of using a raw type here, it's possible to capture
        
// the wildcard but it will require a call to a supplementary
        
// private method
        
final List l = list;
        
l.set(i, l.set(j, l.get(i)));
    
}

    
/**
     
* Swaps the two specified elements in the specified array.
     
*/

    
private static void swap(Object[] arr, int i, int j) {
        
Object tmp = arr[i];
        
arr[i] = arr[j];
        
arr[j] = tmp;
    
}

    
/**
     
* Replaces all of the elements of the specified list with the specified
     
* element. <p>
     
*
     
* This method runs in linear time.
     
*
     
* @param
  
<T> the class of the objects in the list
     
* @param
  
list the list to be filled with the specified element.
     
* @param
  
obj The element with which to fill the specified list.
     
* @throws UnsupportedOperationException if the specified list or its
     
*
         
list-iterator does not support the <tt>set</tt> operation.
     
*/

    
public static <T> void fill(List<? super T> list, T obj) {
        
int size = list.size();

        
if (size < FILL_THRESHOLD || list instanceof RandomAccess) {
            
for (int i=0; i<size; i++)
                
list.set(i, obj);
        
} else {
            
ListIterator<? super T> itr = list.listIterator();
            
for (int i=0; i<size; i++) {
                
itr.next();
                
itr.set(obj);
            
}
        
}
    
}

    
/**
     
* Copies all of the elements from one list into another.
  
After the
     
* operation, the index of each copied element in the destination list
     
* will be identical to its index in the source list.
  
The destination
     
* list must be at least as long as the source list.
  
If it is longer, the
     
* remaining elements in the destination list are unaffected. <p>
     
*
     
* This method runs in linear time.
     
*
     
* @param
  
<T> the class of the objects in the lists
     
* @param
  
dest The destination list.
     
* @param
  
src The source list.
     
* @throws IndexOutOfBoundsException if the destination list is too small
     
*
         
to contain the entire source List.
     
* @throws UnsupportedOperationException if the destination list's
     
*
         
list-iterator does not support the <tt>set</tt> operation.
     
*/

    
public static <T> void copy(List<? super T> dest, List<? extends T> src) {
        
int srcSize = src.size();
        
if (srcSize > dest.size())
            
throw new IndexOutOfBoundsException("Source does not fit in dest");

        
if (srcSize < COPY_THRESHOLD ||
            
(src instanceof RandomAccess && dest instanceof RandomAccess)) {
            
for (int i=0; i<srcSize; i++)
                
dest.set(i, src.get(i));
        
} else {
            
ListIterator<? super T> di=dest.listIterator();
            
ListIterator<? extends T> si=src.listIterator();
            
for (int i=0; i<srcSize; i++) {
                
di.next();
                
di.set(si.next());
            
}
        
}
    
}

    
/**
     
* Returns the minimum element of the given collection, according to the
     
* <i>natural ordering</i> of its elements.
  
All elements in the
     
* collection must implement the <tt>Comparable</tt> interface.
     
* Furthermore, all elements in the collection must be <i>mutually
     
* comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a
     
* <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
     
* <tt>e2</tt> in the collection).<p>
     
*
     
* This method iterates over the entire collection, hence it requires
     
* time proportional to the size of the collection.
     
*
     
* @param
  
<T> the class of the objects in the collection
     
* @param
  
coll the collection whose minimum element is to be determined.
     
* @return the minimum element of the given collection, according
     
*
         
to the <i>natural ordering</i> of its elements.
     
* @throws ClassCastException if the collection contains elements that are
     
*
         
not <i>mutually comparable</i> (for example, strings and
     
*
         
integers).
     
* @throws NoSuchElementException if the collection is empty.
     
* @see Comparable
     
*/

    
public static <T extends Object & Comparable<? super T>> T min(Collection<? extends T> coll) {
        
Iterator<? extends T> i = coll.iterator();
        
T candidate = i.next();

        
while (i.hasNext()) {
            
T next = i.next();
            
if (next.compareTo(candidate) < 0)
                
candidate = next;
        
}
        
return candidate;
    
}

    
/**
     
* Returns the minimum element of the given collection, according to the
     
* order induced by the specified comparator.
  
All elements in the
     
* collection must be <i>mutually comparable</i> by the specified
     
* comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a
     
* <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
     
* <tt>e2</tt> in the collection).<p>
     
*
     
* This method iterates over the entire collection, hence it requires
     
* time proportional to the size of the collection.
     
*
     
* @param
  
<T> the class of the objects in the collection
     
* @param
  
coll the collection whose minimum element is to be determined.
     
* @param
  
comp the comparator with which to determine the minimum element.
     
*
         
A <tt>null</tt> value indicates that the elements' <i>natural
     
*
         
ordering</i> should be used.
     
* @return the minimum element of the given collection, according
     
*
         
to the specified comparator.
     
* @throws ClassCastException if the collection contains elements that are
     
*
         
not <i>mutually comparable</i> using the specified comparator.
     
* @throws NoSuchElementException if the collection is empty.
     
* @see Comparable
     
*/

    
@SuppressWarnings({"unchecked", "rawtypes"})
    
public static <T> T min(Collection<? extends T> coll, Comparator<? super T> comp) {
        
if (comp==null)
            
return (T)min((Collection) coll);

        
Iterator<? extends T> i = coll.iterator();
        
T candidate = i.next();

        
while (i.hasNext()) {
            
T next = i.next();
            
if (comp.compare(next, candidate) < 0)
                
candidate = next;
        
}
        
return candidate;
    
}

    
/**
     
* Returns the maximum element of the given collection, according to the
     
* <i>natural ordering</i> of its elements.
  
All elements in the
     
* collection must implement the <tt>Comparable</tt> interface.
     
* Furthermore, all elements in the collection must be <i>mutually
     
* comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a
     
* <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
     
* <tt>e2</tt> in the collection).<p>
     
*
     
* This method iterates over the entire collection, hence it requires
     
* time proportional to the size of the collection.
     
*
     
* @param
  
<T> the class of the objects in the collection
     
* @param
  
coll the collection whose maximum element is to be determined.
     
* @return the maximum element of the given collection, according
     
*
         
to the <i>natural ordering</i> of its elements.
     
* @throws ClassCastException if the collection contains elements that are
     
*
         
not <i>mutually comparable</i> (for example, strings and
     
*
         
integers).
     
* @throws NoSuchElementException if the collection is empty.
     
* @see Comparable
     
*/

    
public static <T extends Object & Comparable<? super T>> T max(Collection<? extends T> coll) {
        
Iterator<? extends T> i = coll.iterator();
        
T candidate = i.next();

        
while (i.hasNext()) {
            
T next = i.next();
            
if (next.compareTo(candidate) > 0)
                
candidate = next;
        
}
        
return candidate;
    
}

    
/**
     
* Returns the maximum element of the given collection, according to the
     
* order induced by the specified comparator.
  
All elements in the
     
* collection must be <i>mutually comparable</i> by the specified
     
* comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a
     
* <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
     
* <tt>e2</tt> in the collection).<p>
     
*
     
* This method iterates over the entire collection, hence it requires
     
* time proportional to the size of the collection.
     
*
     
* @param
  
<T> the class of the objects in the collection
     
* @param
  
coll the collection whose maximum element is to be determined.
     
* @param
  
comp the comparator with which to determine the maximum element.
     
*
         
A <tt>null</tt> value indicates that the elements' <i>natural
     
*
        
ordering</i> should be used.
     
* @return the maximum element of the given collection, according
     
*
         
to the specified comparator.
     
* @throws ClassCastException if the collection contains elements that are
     
*
         
not <i>mutually comparable</i> using the specified comparator.
     
* @throws NoSuchElementException if the collection is empty.
     
* @see Comparable
     
*/

    
@SuppressWarnings({"unchecked", "rawtypes"})
    
public static <T> T max(Collection<? extends T> coll, Comparator<? super T> comp) {
        
if (comp==null)
            
return (T)max((Collection) coll);

        
Iterator<? extends T> i = coll.iterator();
        
T candidate = i.next();

        
while (i.hasNext()) {
            
T next = i.next();
            
if (comp.compare(next, candidate) > 0)
                
candidate = next;
        
}
        
return candidate;
    
}

    
/**
     
* Rotates the elements in the specified list by the specified distance.
     
* After calling this method, the element at index <tt>i</tt> will be
     
* the element previously at index <tt>(i - distance)</tt> mod
     
* <tt>list.size()</tt>, for all values of <tt>i</tt> between <tt>0</tt>
     
* and <tt>list.size()-1</tt>, inclusive.
  
(This method has no effect on
     
* the size of the list.)
     
*
     
* <p>For example, suppose <tt>list</tt> comprises<tt> [t, a, n, k, s]</tt>.
     
* After invoking <tt>Collections.rotate(list, 1)</tt> (or
     
* <tt>Collections.rotate(list, -4)</tt>), <tt>list</tt> will comprise
     
* <tt>[s, t, a, n, k]</tt>.
     
*
     
* <p>Note that this method can usefully be applied to sublists to
     
* move one or more elements within a list while preserving the
     
* order of the remaining elements.
  
For example, the following idiom
     
* moves the element at index <tt>j</tt> forward to position
     
* <tt>k</tt> (which must be greater than or equal to <tt>j</tt>):
     
* <pre>
     
*Collections.rotate(list.subList(j, k+1), -1);
     
* </pre>
     
* To make this concrete, suppose <tt>list</tt> comprises
     
* <tt>[a, b, c, d, e]</tt>.
  
To move the element at index <tt>1</tt>
     
* (<tt>b</tt>) forward two positions, perform the following invocation:
     
* <pre>
     
*Collections.rotate(l.subList(1, 4), -1);
     
* </pre>
     
* The resulting list is <tt>[a, c, d, b, e]</tt>.
     
*
     
* <p>To move more than one element forward, increase the absolute value
     
* of the rotation distance.
  
To move elements backward, use a positive
     
* shift distance.
     
*
     
* <p>If the specified list is small or implements the {@link
     
* RandomAccess} interface, this implementation exchanges the first
     
* element into the location it should go, and then repeatedly exchanges
     
* the displaced element into the location it should go until a displaced
     
* element is swapped into the first element.
  
If necessary, the process
     
* is repeated on the second and successive elements, until the rotation
     
* is complete.
  
If the specified list is large and doesn't implement the
     
* <tt>RandomAccess</tt> interface, this implementation breaks the
     
* list into two sublist views around index <tt>-distance mod size</tt>.
     
* Then the {@link #reverse(List)} method is invoked on each sublist view,
     
* and finally it is invoked on the entire list.
  
For a more complete
     
* description of both algorithms, see Section 2.3 of Jon Bentley's
     
* <i>Programming Pearls</i> (Addison-Wesley, 1986).
     
*
     
* @param list the list to be rotated.
     
* @param distance the distance to rotate the list.
  
There are no
     
*
        
constraints on this value; it may be zero, negative, or
     
*
        
greater than <tt>list.size()</tt>.
     
* @throws UnsupportedOperationException if the specified list or
     
*
         
its list-iterator does not support the <tt>set</tt> operation.
     
* @since 1.4
     
*/

    
public static void rotate(List<?> list, int distance) {
        
if (list instanceof RandomAccess || list.size() < ROTATE_THRESHOLD)
            
rotate1(list, distance);
        
else
            
rotate2(list, distance);
    
}

    
private static <T> void rotate1(List<T> list, int distance) {
        
int size = list.size();
        
if (size == 0)
            
return;
        
distance = distance % size;
        
if (distance < 0)
            
distance += size;
        
if (distance == 0)
            
return;

        
for (int cycleStart = 0, nMoved = 0; nMoved != size; cycleStart++) {
            
T displaced = list.get(cycleStart);
            
int i = cycleStart;
            
do {
                
i += distance;
                
if (i >= size)
                    
i -= size;
                
displaced = list.set(i, displaced);
                
nMoved ++;
            
} while (i != cycleStart);
        
}
    
}

    
private static void rotate2(List<?> list, int distance) {
        
int size = list.size();
        
if (size == 0)
            
return;
        
int mid =
  
-distance % size;
        
if (mid < 0)
            
mid += size;
        
if (mid == 0)
            
return;

        
reverse(list.subList(0, mid));
        
reverse(list.subList(mid, size));
        
reverse(list);
    
}

    
/**
     
* Replaces all occurrences of one specified value in a list with another.
     
* More formally, replaces with <tt>newVal</tt> each element <tt>e</tt>
     
* in <tt>list</tt> such that
     
* <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>.
     
* (This method has no effect on the size of the list.)
     
*
     
* @param
  
<T> the class of the objects in the list
     
* @param list the list in which replacement is to occur.
     
* @param oldVal the old value to be replaced.
     
* @param newVal the new value with which <tt>oldVal</tt> is to be
     
*
        
replaced.
     
* @return <tt>true</tt> if <tt>list</tt> contained one or more elements
     
*
         
<tt>e</tt> such that
     
*
         
<tt>(oldVal==null ?
  
e==null : oldVal.equals(e))</tt>.
     
* @throws UnsupportedOperationException if the specified list or
     
*
         
its list-iterator does not support the <tt>set</tt> operation.
     
* @since
  
1.4
     
*/

    
public static <T> boolean replaceAll(List<T> list, T oldVal, T newVal) {
        
boolean result = false;
        
int size = list.size();
        
if (size < REPLACEALL_THRESHOLD || list instanceof RandomAccess) {
            
if (oldVal==null) {
                
for (int i=0; i<size; i++) {
                    
if (list.get(i)==null) {
                        
list.set(i, newVal);
                        
result = true;
                    
}
                
}
            
} else {
                
for (int i=0; i<size; i++) {
                    
if (oldVal.equals(list.get(i))) {
                        
list.set(i, newVal);
                        
result = true;
                    
}
                
}
            
}
        
} else {
            
ListIterator<T> itr=list.listIterator();
            
if (oldVal==null) {
                
for (int i=0; i<size; i++) {
                    
if (itr.next()==null) {
                        
itr.set(newVal);
                        
result = true;
                    
}
                
}
            
} else {
                
for (int i=0; i<size; i++) {
                    
if (oldVal.equals(itr.next())) {
                        
itr.set(newVal);
                        
result = true;
                    
}
                
}
            
}
        
}
        
return result;
    
}

    
/**
     
* Returns the starting position of the first occurrence of the specified
     
* target list within the specified source list, or -1 if there is no
     
* such occurrence.
  
More formally, returns the lowest index <tt>i</tt>
     
* such that {@code source.subList(i, i+target.size()).equals(target)},
     
* or -1 if there is no such index.
  
(Returns -1 if
     
* {@code target.size() > source.size()})
     
*
     
* <p>This implementation uses the "brute force" technique of scanning
     
* over the source list, looking for a match with the target at each
     
* location in turn.
     
*
     
* @param source the list in which to search for the first occurrence
     
*
        
of <tt>target</tt>.
     
* @param target the list to search for as a subList of <tt>source</tt>.
     
* @return the starting position of the first occurrence of the specified
     
*
         
target list within the specified source list, or -1 if there
     
*
         
is no such occurrence.
     
* @since
  
1.4
     
*/

    
public static int indexOfSubList(List<?> source, List<?> target) {
        
int sourceSize = source.size();
        
int targetSize = target.size();
        
int maxCandidate = sourceSize - targetSize;

        
if (sourceSize < INDEXOFSUBLIST_THRESHOLD ||
            
(source instanceof RandomAccess&&target instanceof RandomAccess)) {
        
nextCand:
            
for (int candidate = 0; candidate <= maxCandidate; candidate++) {
                
for (int i=0, j=candidate; i<targetSize; i++, j++)
                    
if (!eq(target.get(i), source.get(j)))
                        
continue nextCand;
  
// Element mismatch, try next cand
                
return candidate;
  
// All elements of candidate matched target
            
}
        
} else {
  
// Iterator version of above algorithm
            
ListIterator<?> si = source.listIterator();
        
nextCand:
            
for (int candidate = 0; candidate <= maxCandidate; candidate++) {
                
ListIterator<?> ti = target.listIterator();
                
for (int i=0; i<targetSize; i++) {
                    
if (!eq(ti.next(), si.next())) {
                        
// Back up source iterator to next candidate
                        
for (int j=0; j<i; j++)
                            
si.previous();
                        
continue nextCand;
                    
}
                
}
                
return candidate;
            
}
        
}
        
return -1;
  
// No candidate matched the target
    
}

    
/**
     
* Returns the starting position of the last occurrence of the specified
     
* target list within the specified source list, or -1 if there is no such
     
* occurrence.
  
More formally, returns the highest index <tt>i</tt>
     
* such that {@code source.subList(i, i+target.size()).equals(target)},
     
* or -1 if there is no such index.
  
(Returns -1 if
     
* {@code target.size() > source.size()})
     
*
     
* <p>This implementation uses the "brute force" technique of iterating
     
* over the source list, looking for a match with the target at each
     
* location in turn.
     
*
     
* @param source the list in which to search for the last occurrence
     
*
        
of <tt>target</tt>.
     
* @param target the list to search for as a subList of <tt>source</tt>.
     
* @return the starting position of the last occurrence of the specified
     
*
         
target list within the specified source list, or -1 if there
     
*
         
is no such occurrence.
     
* @since
  
1.4
     
*/

    
public static int lastIndexOfSubList(List<?> source, List<?> target) {
        
int sourceSize = source.size();
        
int targetSize = target.size();
        
int maxCandidate = sourceSize - targetSize;

        
if (sourceSize < INDEXOFSUBLIST_THRESHOLD ||
            
source instanceof RandomAccess) {
   
// Index access version
        
nextCand:
            
for (int candidate = maxCandidate; candidate >= 0; candidate--) {
                
for (int i=0, j=candidate; i<targetSize; i++, j++)
                    
if (!eq(target.get(i), source.get(j)))
                        
continue nextCand;
  
// Element mismatch, try next cand
                
return candidate;
  
// All elements of candidate matched target
            
}
        
} else {
  
// Iterator version of above algorithm
            
if (maxCandidate < 0)
                
return -1;
            
ListIterator<?> si = source.listIterator(maxCandidate);
        
nextCand:
            
for (int candidate = maxCandidate; candidate >= 0; candidate--) {
                
ListIterator<?> ti = target.listIterator();
                
for (int i=0; i<targetSize; i++) {
                    
if (!eq(ti.next(), si.next())) {
                        
if (candidate != 0) {
                            
// Back up source iterator to next candidate
                            
for (int j=0; j<=i+1; j++)
                                
si.previous();
                        
}
                        
continue nextCand;
                    
}
                
}
                
return candidate;
            
}
        
}
        
return -1;
  
// No candidate matched the target
    
}


    
// Unmodifiable Wrappers

    
/**
     
* Returns an unmodifiable view of the specified collection.
  
This method
     
* allows modules to provide users with "read-only" access to internal
     
* collections.
  
Query operations on the returned collection "read through"
     
* to the specified collection, and attempts to modify the returned
     
* collection, whether direct or via its iterator, result in an
     
* <tt>UnsupportedOperationException</tt>.<p>
     
*
     
* The returned collection does <i>not</i> pass the hashCode and equals
     
* operations through to the backing collection, but relies on
     
* <tt>Object</tt>'s <tt>equals</tt> and <tt>hashCode</tt> methods.
  
This
     
* is necessary to preserve the contracts of these operations in the case
     
* that the backing collection is a set or a list.<p>
     
*
     
* The returned collection will be serializable if the specified collection
     
* is serializable.
     
*
     
* @param
  
<T> the class of the objects in the collection
     
* @param
  
c the collection for which an unmodifiable view is to be
     
*
         
returned.
     
* @return an unmodifiable view of the specified collection.
     
*/

    
public static <T> Collection<T> unmodifiableCollection(Collection<? extends T> c) {
        
return new UnmodifiableCollection<>(c);
    
}

    
/**
     
* @serial include
     
*/
    
static class UnmodifiableCollection<E> implements Collection<E>, Serializable {
        
private static final long serialVersionUID = 1820017752578914078L;

        
final Collection<? extends E> c;

        
UnmodifiableCollection(Collection<? extends E> c) {
            
if (c==null)
                
throw new NullPointerException();
            
this.c = c;
        
}

        
public int size()
                   
{return c.size();}
        
public boolean isEmpty()
            
{return c.isEmpty();}
        
public boolean contains(Object o)
   
{return c.contains(o);}
        
public Object[] toArray()
           
{return c.toArray();}
        
public <T> T[] toArray(T[] a)
       
{return c.toArray(a);}
        
public String toString()
            
{return c.toString();}

        
public Iterator<E> iterator() {
            
return new Iterator<E>() {
                
private final Iterator<? extends E> i = c.iterator();

                
public boolean hasNext() {return i.hasNext();}
                
public E next()
          
{return i.next();}
                
public void remove() {
                    
throw new UnsupportedOperationException();
                
}
                
@Override
                
public void forEachRemaining(Consumer<? super E> action) {
                    
// Use backing collection version
                    
i.forEachRemaining(action);
                
}
            
};
        
}

        
public boolean add(E e) {
            
throw new UnsupportedOperationException();
        
}
        
public boolean remove(Object o) {
            
throw new UnsupportedOperationException();
        
}

        
public boolean containsAll(Collection<?> coll) {
            
return c.containsAll(coll);
        
}
        
public boolean addAll(Collection<? extends E> coll) {
            
throw new UnsupportedOperationException();
        
}
        
public boolean removeAll(Collection<?> coll) {
            
throw new UnsupportedOperationException();
        
}
        
public boolean retainAll(Collection<?> coll) {
            
throw new UnsupportedOperationException();
        
}
        
public void clear() {
            
throw new UnsupportedOperationException();
        
}

        
// Override default methods in Collection
        
@Override
        
public void forEach(Consumer<? super E> action) {
            
c.forEach(action);
        
}
        
@Override
        
public boolean removeIf(Predicate<? super E> filter) {
            
throw new UnsupportedOperationException();
        
}
        
@SuppressWarnings("unchecked")
        
@Override
        
public Spliterator<E> spliterator() {
            
return (Spliterator<E>)c.spliterator();
        
}
        
@SuppressWarnings("unchecked")
        
@Override
        
public Stream<E> stream() {
            
return (Stream<E>)c.stream();
        
}
        
@SuppressWarnings("unchecked")
        
@Override
        
public Stream<E> parallelStream() {
            
return (Stream<E>)c.parallelStream();
        
}
    
}

    
/**
     
* Returns an unmodifiable view of the specified set.
  
This method allows
     
* modules to provide users with "read-only" access to internal sets.
     
* Query operations on the returned set "read through" to the specified
     
* set, and attempts to modify the returned set, whether direct or via its
     
* iterator, result in an <tt>UnsupportedOperationException</tt>.<p>
     
*
     
* The returned set will be serializable if the specified set
     
* is serializable.
     
*
     
* @param
  
<T> the class of the objects in the set
     
* @param
  
s the set for which an unmodifiable view is to be returned.
     
* @return an unmodifiable view of the specified set.
     
*/

    
public static <T> Set<T> unmodifiableSet(Set<? extends T> s) {
        
return new UnmodifiableSet<>(s);
    
}

    
/**
     
* @serial include
     
*/
    
static class UnmodifiableSet<E> extends UnmodifiableCollection<E>
                                 
implements Set<E>, Serializable {
        
private static final long serialVersionUID = -9215047833775013803L;

        
UnmodifiableSet(Set<? extends E> s)
     
{super(s);}
        
public boolean equals(Object o) {return o == this || c.equals(o);}
        
public int hashCode()
           
{return c.hashCode();}
    
}

    
/**
     
* Returns an unmodifiable view of the specified sorted set.
  
This method
     
* allows modules to provide users with "read-only" access to internal
     
* sorted sets.
  
Query operations on the returned sorted set "read
     
* through" to the specified sorted set.
  
Attempts to modify the returned
     
* sorted set, whether direct, via its iterator, or via its
     
* <tt>subSet</tt>, <tt>headSet</tt>, or <tt>tailSet</tt> views, result in
     
* an <tt>UnsupportedOperationException</tt>.<p>
     
*
     
* The returned sorted set will be serializable if the specified sorted set
     
* is serializable.
     
*
     
* @param
  
<T> the class of the objects in the set
     
* @param s the sorted set for which an unmodifiable view is to be
     
*
        
returned.
     
* @return an unmodifiable view of the specified sorted set.
     
*/

    
public static <T> SortedSet<T> unmodifiableSortedSet(SortedSet<T> s) {
        
return new UnmodifiableSortedSet<>(s);
    
}

    
/**
     
* @serial include
     
*/
    
static class UnmodifiableSortedSet<E>
                             
extends UnmodifiableSet<E>
                             
implements SortedSet<E>, Serializable {
        
private static final long serialVersionUID = -4929149591599911165L;
        
private final SortedSet<E> ss;

        
UnmodifiableSortedSet(SortedSet<E> s) {super(s); ss = s;}

        
public Comparator<? super E> comparator() {return ss.comparator();}

        
public SortedSet<E> subSet(E fromElement, E toElement) {
            
return new UnmodifiableSortedSet<>(ss.subSet(fromElement,toElement));
        
}
        
public SortedSet<E> headSet(E toElement) {
            
return new UnmodifiableSortedSet<>(ss.headSet(toElement));
        
}
        
public SortedSet<E> tailSet(E fromElement) {
            
return new UnmodifiableSortedSet<>(ss.tailSet(fromElement));
        
}

        
public E first()
                   
{return ss.first();}
        
public E last()
                    
{return ss.last();}
    
}

    
/**
     
* Returns an unmodifiable view of the specified navigable set.
  
This method
     
* allows modules to provide users with "read-only" access to internal
     
* navigable sets.
  
Query operations on the returned navigable set "read
     
* through" to the specified navigable set.
  
Attempts to modify the returned
     
* navigable set, whether direct, via its iterator, or via its
     
* {@code subSet}, {@code headSet}, or {@code tailSet} views, result in
     
* an {@code UnsupportedOperationException}.<p>
     
*
     
* The returned navigable set will be serializable if the specified
     
* navigable set is serializable.
     
*
     
* @param
  
<T> the class of the objects in the set
     
* @param s the navigable set for which an unmodifiable view is to be
     
*
        
returned
     
* @return an unmodifiable view of the specified navigable set
     
* @since 1.8
     
*/

    
public static <T> NavigableSet<T> unmodifiableNavigableSet(NavigableSet<T> s) {
        
return new UnmodifiableNavigableSet<>(s);
    
}

    
/**
     
* Wraps a navigable set and disables all of the mutative operations.
     
*
     
* @param <E> type of elements
     
* @serial include
     
*/

    
static class UnmodifiableNavigableSet<E>
                             
extends UnmodifiableSortedSet<E>
                             
implements NavigableSet<E>, Serializable {

        
private static final long serialVersionUID = -6027448201786391929L;

        
/**
         
* A singleton empty unmodifiable navigable set used for
         
*
 
.
         
*
         
* @param <E> type of elements, if there were any, and bounds
         
*/

        
private static class EmptyNavigableSet<E> extends UnmodifiableNavigableSet<E>
            
implements Serializable {
            
private static final long serialVersionUID = -6291252904449939134L;

            
public EmptyNavigableSet() {
                
super(new TreeSet<E>());
            
}

            
private Object readResolve()
        
{ return EMPTY_NAVIGABLE_SET; }
        
}

        
@SuppressWarnings("rawtypes")
        
private static final NavigableSet<?> EMPTY_NAVIGABLE_SET =
                
new EmptyNavigableSet<>();

        
/**
         
* The instance we are protecting.
         
*/
        
private final NavigableSet<E> ns;

        
UnmodifiableNavigableSet(NavigableSet<E> s)
         
{super(s); ns = s;}

        
public E lower(E e)
                             
{ return ns.lower(e); }
        
public E floor(E e)
                             
{ return ns.floor(e); }
        
public E ceiling(E e)
                         
{ return ns.ceiling(e); }
        
public E higher(E e)
                           
{ return ns.higher(e); }
        
public E pollFirst()
     
{ throw new UnsupportedOperationException(); }
        
public E pollLast()
      
{ throw new UnsupportedOperationException(); }
        
public NavigableSet<E> descendingSet()
                 
{ return new UnmodifiableNavigableSet<>(ns.descendingSet()); }
        
public Iterator<E> descendingIterator()
                                         
{ return descendingSet().iterator(); }

        
public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
            
return new UnmodifiableNavigableSet<>(
                
ns.subSet(fromElement, fromInclusive, toElement, toInclusive));
        
}

        
public NavigableSet<E> headSet(E toElement, boolean inclusive) {
            
return new UnmodifiableNavigableSet<>(
                
ns.headSet(toElement, inclusive));
        
}

        
public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
            
return new UnmodifiableNavigableSet<>(
                
ns.tailSet(fromElement, inclusive));
        
}
    
}

    
/**
     
* Returns an unmodifiable view of the specified list.
  
This method allows
     
* modules to provide users with "read-only" access to internal
     
* lists.
  
Query operations on the returned list "read through" to the
     
* specified list, and attempts to modify the returned list, whether
     
* direct or via its iterator, result in an
     
* <tt>UnsupportedOperationException</tt>.<p>
     
*
     
* The returned list will be serializable if the specified list
     
* is serializable. Similarly, the returned list will implement
     
* {@link RandomAccess} if the specified list does.
     
*
     
* @param
  
<T> the class of the objects in the list
     
* @param
  
list the list for which an unmodifiable view is to be returned.
     
* @return an unmodifiable view of the specified list.
     
*/

    
public static <T> List<T> unmodifiableList(List<? extends T> list) {
        
return (list instanceof RandomAccess ?
                
new UnmodifiableRandomAccessList<>(list) :
                
new UnmodifiableList<>(list));
    
}

    
/**
     
* @serial include
     
*/
    
static class UnmodifiableList<E> extends UnmodifiableCollection<E>
                                  
implements List<E> {
        
private static final long serialVersionUID = -283967356065247728L;

        
final List<? extends E> list;

        
UnmodifiableList(List<? extends E> list) {
            
super(list);
            
this.list = list;
        
}

        
public boolean equals(Object o) {return o == this || list.equals(o);}
        
public int hashCode()
           
{return list.hashCode();}

        
public E get(int index) {return list.get(index);}
        
public E set(int index, E element) {
            
throw new UnsupportedOperationException();
        
}
        
public void add(int index, E element) {
            
throw new UnsupportedOperationException();
        
}
        
public E remove(int index) {
            
throw new UnsupportedOperationException();
        
}
        
public int indexOf(Object o)
            
{return list.indexOf(o);}
        
public int lastIndexOf(Object o)
        
{return list.lastIndexOf(o);}
        
public boolean addAll(int index, Collection<? extends E> c) {
            
throw new UnsupportedOperationException();
        
}

        
@Override
        
public void replaceAll(UnaryOperator<E> operator) {
            
throw new UnsupportedOperationException();
        
}
        
@Override
        
public void sort(Comparator<? super E> c) {
            
throw new UnsupportedOperationException();
        
}

        
public ListIterator<E> listIterator()
   
{return listIterator(0);}

        
public ListIterator<E> listIterator(final int index) {
            
return new ListIterator<E>() {
                
private final ListIterator<? extends E> i
                    
= list.listIterator(index);

                
public boolean hasNext()
     
{return i.hasNext();}
                
public E next()
              
{return i.next();}
                
public boolean hasPrevious() {return i.hasPrevious();}
                
public E previous()
          
{return i.previous();}
                
public int nextIndex()
       
{return i.nextIndex();}
                
public int previousIndex()
   
{return i.previousIndex();}

                
public void remove() {
                    
throw new UnsupportedOperationException();
                
}
                
public void set(E e) {
                    
throw new UnsupportedOperationException();
                
}
                
public void add(E e) {
                    
throw new UnsupportedOperationException();
                
}

                
@Override
                
public void forEachRemaining(Consumer<? super E> action) {
                    
i.forEachRemaining(action);
                
}
            
};
        
}

        
public List<E> subList(int fromIndex, int toIndex) {
            
return new UnmodifiableList<>(list.subList(fromIndex, toIndex));
        
}

        
/**
         
* UnmodifiableRandomAccessList instances are serialized as
         
* UnmodifiableList instances to allow them to be deserialized
         
* in pre-1.4 JREs (which do not have UnmodifiableRandomAccessList).
         
* This method inverts the transformation.
  
As a beneficial
         
* side-effect, it also grafts the RandomAccess marker onto
         
* UnmodifiableList instances that were serialized in pre-1.4 JREs.
         
*
         
* Note: Unfortunately, UnmodifiableRandomAccessList instances
         
* serialized in 1.4.1 and deserialized in 1.4 will become
         
* UnmodifiableList instances, as this method was missing in 1.4.
         
*/

        
private Object readResolve() {
            
return (list instanceof RandomAccess
                    
? new UnmodifiableRandomAccessList<>(list)
                    
: this);
        
}
    
}

    
/**
     
* @serial include
     
*/
    
static class UnmodifiableRandomAccessList<E> extends UnmodifiableList<E>
                                              
implements RandomAccess
    
{
        
UnmodifiableRandomAccessList(List<? extends E> list) {
            
super(list);
        
}

        
public List<E> subList(int fromIndex, int toIndex) {
            
return new UnmodifiableRandomAccessList<>(
                
list.subList(fromIndex, toIndex));
        
}

        
private static final long serialVersionUID = -2542308836966382001L;

        
/**
         
* Allows instances to be deserialized in pre-1.4 JREs (which do
         
* not have UnmodifiableRandomAccessList).
  
UnmodifiableList has
         
* a readResolve method that inverts this transformation upon
         
* deserialization.
         
*/

        
private Object writeReplace() {
            
return new UnmodifiableList<>(list);
        
}
    
}

    
/**
     
* Returns an unmodifiable view of the specified map.
  
This method
     
* allows modules to provide users with "read-only" access to internal
     
* maps.
  
Query operations on the returned map "read through"
     
* to the specified map, and attempts to modify the returned
     
* map, whether direct or via its collection views, result in an
     
* <tt>UnsupportedOperationException</tt>.<p>
     
*
     
* The returned map will be serializable if the specified map
     
* is serializable.
     
*
     
* @param <K> the class of the map keys
     
* @param <V> the class of the map values
     
* @param
  
m the map for which an unmodifiable view is to be returned.
     
* @return an unmodifiable view of the specified map.
     
*/

    
public static <K,V> Map<K,V> unmodifiableMap(Map<? extends K, ? extends V> m) {
        
return new UnmodifiableMap<>(m);
    
}

    
/**
     
* @serial include
     
*/
    
private static class UnmodifiableMap<K,V> implements Map<K,V>, Serializable {
        
private static final long serialVersionUID = -1034234728574286014L;

        
private final Map<? extends K, ? extends V> m;

        
UnmodifiableMap(Map<? extends K, ? extends V> m) {
            
if (m==null)
                
throw new NullPointerException();
            
this.m = m;
        
}

        
public int size()
                        
{return m.size();}
        
public boolean isEmpty()
                 
{return m.isEmpty();}
        
public boolean containsKey(Object key)
   
{return m.containsKey(key);}
        
public boolean containsValue(Object val) {return m.containsValue(val);}
        
public V get(Object key)
                 
{return m.get(key);}

        
public V put(K key, V value) {
            
throw new UnsupportedOperationException();
        
}
        
public V remove(Object key) {
            
throw new UnsupportedOperationException();
        
}
        
public void putAll(Map<? extends K, ? extends V> m) {
            
throw new UnsupportedOperationException();
        
}
        
public void clear() {
            
throw new UnsupportedOperationException();
        
}

        
private transient Set<K> keySet;
        
private transient Set<Map.Entry<K,V>> entrySet;
        
private transient Collection<V> values;

        
public Set<K> keySet() {
            
if (keySet==null)
                
keySet = unmodifiableSet(m.keySet());
            
return keySet;
        
}

        
public Set<Map.Entry<K,V>> entrySet() {
            
if (entrySet==null)
                
entrySet = new UnmodifiableEntrySet<>(m.entrySet());
            
return entrySet;
        
}

        
public Collection<V> values() {
            
if (values==null)
                
values = unmodifiableCollection(m.values());
            
return values;
        
}

        
public boolean equals(Object o) {return o == this || m.equals(o);}
        
public int hashCode()
           
{return m.hashCode();}
        
public String toString()
        
{return m.toString();}

        
// Override default methods in Map
        
@Override
        
@SuppressWarnings("unchecked")
        
public V getOrDefault(Object k, V defaultValue) {
            
// Safe cast as we don't change the value
            
return ((Map<K, V>)m).getOrDefault(k, defaultValue);
        
}

        
@Override
        
public void forEach(BiConsumer<? super K, ? super V> action) {
            
m.forEach(action);
        
}

        
@Override
        
public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
            
throw new UnsupportedOperationException();
        
}

        
@Override
        
public V putIfAbsent(K key, V value) {
            
throw new UnsupportedOperationException();
        
}

        
@Override
        
public boolean remove(Object key, Object value) {
            
throw new UnsupportedOperationException();
        
}

        
@Override
        
public boolean replace(K key, V oldValue, V newValue) {
            
throw new UnsupportedOperationException();
        
}

        
@Override
        
public V replace(K key, V value) {
            
throw new UnsupportedOperationException();
        
}

        
@Override
        
public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
            
throw new UnsupportedOperationException();
        
}

        
@Override
        
public V computeIfPresent(K key,
                
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
            
throw new UnsupportedOperationException();
        
}

        
@Override
        
public V compute(K key,
                
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
            
throw new UnsupportedOperationException();
        
}

        
@Override
        
public V merge(K key, V value,
                
BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
            
throw new UnsupportedOperationException();
        
}

        
/**
         
* We need this class in addition to UnmodifiableSet as
         
* Map.Entries themselves permit modification of the backing Map
         
* via their setValue operation.
  
This class is subtle: there are
         
* many possible attacks that must be thwarted.
         
*
         
* @serial include
         
*/

        
static class UnmodifiableEntrySet<K,V>
            
extends UnmodifiableSet<Map.Entry<K,V>> {
            
private static final long serialVersionUID = 7854390611657943733L;

            
@SuppressWarnings({"unchecked", "rawtypes"})
            
UnmodifiableEntrySet(Set<? extends Map.Entry<? extends K, ? extends V>> s) {
                
// Need to cast to raw in order to work around a limitation in the type system
                
super((Set)s);
            
}

            
static <K, V> Consumer<Map.Entry<K, V>> entryConsumer(Consumer<? super Entry<K, V>> action) {
                
return e -> action.accept(new UnmodifiableEntry<>(e));
            
}

            
public void forEach(Consumer<? super Entry<K, V>> action) {
                
Objects.requireNonNull(action);
                
c.forEach(entryConsumer(action));
            
}

            
static final class UnmodifiableEntrySetSpliterator<K, V>
                    
implements Spliterator<Entry<K,V>> {
                
final Spliterator<Map.Entry<K, V>> s;

                
UnmodifiableEntrySetSpliterator(Spliterator<Entry<K, V>