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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 
*
 
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* 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).
 
*
 
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* 2 along with this work; if not, write to the Free Software Foundation,
 
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 
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*/
package java.util.function;

import java.util.Objects;

/**
 
* Represents a function that accepts one argument and produces a result.
 
*
 
* <p>This is a<a href="package-summary.html">functional interface</a>
 
* whose functional method is {@link #apply(Object)}.
 
*
 
* @param <T> the type of the input to the function
 
* @param <R> the type of the result of the function
 
*
 
* @since 1.8
 
*/

@FunctionalInterface
public interface Function<T, R> {

    
/**
     
* Applies this function to the given argument.
     
*
     
* @param t the function argument
     
* @return the function result
     
*/

    
R apply(T t);

    
/**
     
* Returns a composed function that first applies the {@code before}
     
* function to its input, and then applies this function to the result.
     
* If evaluation of either function throws an exception, it is relayed to
     
* the caller of the composed function.
     
*
     
* @param <V> the type of input to the {@code before} function, and to the
     
*
           
composed function
     
* @param before the function to apply before this function is applied
     
* @return a composed function that first applies the {@code before}
     
* function and then applies this function
     
* @throws NullPointerException if before is null
     
*
     
* @see #andThen(Function)
     
*/

    
default <V> Function<V, R> compose(Function<? super V, ? extends T> before) {
        
Objects.requireNonNull(before);
        
return (V v) -> apply(before.apply(v));
    
}

    
/**
     
* Returns a composed function that first applies this function to
     
* its input, and then applies the {@code after} function to the result.
     
* If evaluation of either function throws an exception, it is relayed to
     
* the caller of the composed function.
     
*
     
* @param <V> the type of output of the {@code after} function, and of the
     
*
           
composed function
     
* @param after the function to apply after this function is applied
     
* @return a composed function that first applies this function and then
     
* applies the {@code after} function
     
* @throws NullPointerException if after is null
     
*
     
* @see #compose(Function)
     
*/

    
default <V> Function<T, V> andThen(Function<? super R, ? extends V> after) {
        
Objects.requireNonNull(after);
        
return (T t) -> after.apply(apply(t));
    
}

    
/**
     
* Returns a function that always returns its input argument.
     
*
     
* @param <T> the type of the input and output objects to the function
     
* @return a function that always returns its input argument
     
*/

    
static <T> Function<T, T> identity() {
        
return t -> t;
    
}
}