com.google.common.base.Function Maven / Gradle / Ivy
/*
* 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 com.google.common.annotations.GwtCompatible;
import javax.annotation.Nullable;
/**
* Determines an output value based on an input value.
*
* The {@link Functions} class provides common functions and related utilites.
*
*
See the Guava User Guide article on the use of {@code
* Function}.
*
* @author Kevin Bourrillion
* @since 2.0 (imported from Google Collections Library)
*/
@GwtCompatible
public interface Function {
/**
* Returns the result of applying this function to {@code input}. This method is generally
* expected, but not absolutely required, to have the following properties:
*
*
* - Its execution does not cause any observable side effects.
*
- The computation is consistent with equals; that is, {@link Objects#equal
* Objects.equal}{@code (a, b)} implies that {@code Objects.equal(function.apply(a),
* function.apply(b))}.
*
*
* @throws NullPointerException if {@code input} is null and this function does not accept null
* arguments
*/
@Nullable T apply(@Nullable F input);
/**
* Indicates whether another object is equal to this function.
*
* Most implementations will have no reason to override the behavior of {@link Object#equals}.
* However, an implementation may also choose to return {@code true} whenever {@code object} is a
* {@link Function} that it considers interchangeable with this one. "Interchangeable"
* typically means that {@code Objects.equal(this.apply(f), that.apply(f))} is true for all
* {@code f} of type {@code F}. Note that a {@code false} result from this method does not imply
* that the functions are known not to be interchangeable.
*/
@Override
boolean equals(@Nullable Object object);
}