/* * Copyright (C) 2007 The Guava Authors * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.google.common.base; import static com.google.common.base.Preconditions.checkArgument; import static com.google.common.base.Preconditions.checkNotNull; import com.google.common.annotations.Beta; import com.google.common.annotations.GwtCompatible; import java.io.Serializable; import java.util.Map; import javax.annotation.Nullable; /** * Static utility methods pertaining to {@code Function} instances. * *
All methods return serializable functions as long as they're given serializable parameters. * *
See the Guava User Guide article on the use of {@code * Function}. * * @author Mike Bostock * @author Jared Levy * @since 2.0 (imported from Google Collections Library) */ @GwtCompatible public final class Functions { private Functions() {} /** * Returns a function that calls {@code toString()} on its argument. The function does not accept * nulls; it will throw a {@link NullPointerException} when applied to {@code null}. * *
Warning: The returned function may not be consistent with equals (as * documented at {@link Function#apply}). For example, this function yields different results for * the two equal instances {@code ImmutableSet.of(1, 2)} and {@code ImmutableSet.of(2, 1)}. */ public static Function