/*
 
* Copyright (c) 1997, 2013, 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.util.function.Consumer;

/**
 
* An iterator over a collection.
  
{@code Iterator} takes the place of
 
* {@link Enumeration} in the Java Collections Framework.
  
Iterators
 
* differ from enumerations in two ways:
 
*
 
* <ul>
 
*
      
<li> Iterators allow the caller to remove elements from the
 
*
           
underlying collection during the iteration with well-defined
 
*
           
semantics.
 
*
      
<li> Method names have been improved.
 
* </ul>
 
*
 
* <p>This interface is a member of the
 
* <a href="{@docRoot}/../technotes/guides/collections/index.html">
 
* Java Collections Framework</a>.
 
*
 
* @param <E> the type of elements returned by this iterator
 
*
 
* @author
  
Josh Bloch
 
* @see Collection
 
* @see ListIterator
 
* @see Iterable
 
* @since 1.2
 
*/

public interface Iterator<E> {
    
/**
     
* Returns {@code true} if the iteration has more elements.
     
* (In other words, returns {@code true} if {@link #next} would
     
* return an element rather than throwing an exception.)
     
*
     
* @return {@code true} if the iteration has more elements
     
*/

    
boolean hasNext();

    
/**
     
* Returns the next element in the iteration.
     
*
     
* @return the next element in the iteration
     
* @throws NoSuchElementException if the iteration has no more elements
     
*/

    
E next();

    
/**
     
* Removes from the underlying collection the last element returned
     
* by this iterator (optional operation).
  
This method can be called
     
* only once per call to {@link #next}.
  
The behavior of an iterator
     
* is unspecified if the underlying collection is modified while the
     
* iteration is in progress in any way other than by calling this
     
* method.
     
*
     
* @implSpec
     
* The default implementation throws an instance of
     
* {@link UnsupportedOperationException} and performs no other action.
     
*
     
* @throws UnsupportedOperationException if the {@code remove}
     
*
         
operation is not supported by this iterator
     
*
     
* @throws IllegalStateException if the {@code next} method has not
     
*
         
yet been called, or the {@code remove} method has already
     
*
         
been called after the last call to the {@code next}
     
*
         
method
     
*/

    
default void remove() {
        
throw new UnsupportedOperationException("remove");
    
}

    
/**
     
* Performs the given action for each remaining element until all elements
     
* have been processed or the action throws an exception.
  
Actions are
     
* performed in the order of iteration, if that order is specified.
     
* Exceptions thrown by the action are relayed to the caller.
     
*
     
* @implSpec
     
* <p>The default implementation behaves as if:
     
* <pre>{@code
     
*while (hasNext())
     
*
         
action.accept(next());
     
* }</pre>
     
*
     
* @param action The action to be performed for each element
     
* @throws NullPointerException if the specified action is null
     
* @since 1.8
     
*/

    
default void forEachRemaining(Consumer<? super E> action) {
        
Objects.requireNonNull(action);
        
while (hasNext())
            
action.accept(next());
    
}
}