| /* |
| * Copyright (c) 2010, 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.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; |
| } |
| } |