openjdk/jdk/src/share/classes/java/util/function/Function.java

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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,
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package java.util.function;

/**
 * Apply a function to the input object yielding an appropriate result object. A
 * function may variously provide a mapping between types, object instances or
 * keys and values or any other form of transformation upon the input.
 *
 * @param <T> the type of input objects to the {@code apply} operation
 * @param <R> the type of result objects from the {@code apply} operation. May
 * be the same type as {@code <T>}.
 *
 * @since 1.8
 */
@FunctionalInterface
public interface Function<T, R> {

    /**
     * Yield an appropriate result object for the input object.
     *
     * @param t the input object
     * @return the function result
     */
    public R apply(T t);
}