75 lines
2.5 KiB
Java
75 lines
2.5 KiB
Java
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/*
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* Copyright (C) 2007 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.common.base;
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import javax.annotation.Nullable;
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import com.google.common.annotations.GwtCompatible;
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/**
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* Determines an output value based on an input value.
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*
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* <p>
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* The {@link Functions} class provides common functions and related utilites.
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*
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* <p>
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* See the Guava User Guide article on <a href=
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* "http://code.google.com/p/guava-libraries/wiki/FunctionalExplained">the use
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* of {@code
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* Function}</a>.
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*
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* @author Kevin Bourrillion
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* @since 2.0 (imported from Google Collections Library)
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*/
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@GwtCompatible
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public interface Function<F, T> {
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/**
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* Returns the result of applying this function to {@code input}. This method is
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* <i>generally expected</i>, but not absolutely required, to have the following
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* properties:
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*
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* <ul>
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* <li>Its execution does not cause any observable side effects.
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* <li>The computation is <i>consistent with equals</i>; that is,
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* {@link Objects#equal Objects.equal}{@code (a, b)} implies that
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* {@code Objects.equal(function.apply(a),
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* function.apply(b))}.
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* </ul>
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*
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* @throws NullPointerException if {@code input} is null and this function does
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* not accept null arguments
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*/
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@Nullable
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T apply(@Nullable F input);
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/**
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* Indicates whether another object is equal to this function.
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*
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* <p>
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* Most implementations will have no reason to override the behavior of
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* {@link Object#equals}. However, an implementation may also choose to return
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* {@code true} whenever {@code object} is a {@link Function} that it considers
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* <i>interchangeable</i> with this one. "Interchangeable" <i>typically</i>
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* means that {@code Objects.equal(this.apply(f), that.apply(f))} is true for
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* all {@code f} of type {@code F}. Note that a {@code false} result from this
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* method does not imply that the functions are known <i>not</i> to be
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* interchangeable.
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*/
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@Override
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boolean equals(@Nullable Object object);
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}
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