Java example source code file (Immutable.java)

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Java tags/keywords

annotation, documented, immutable, runtime, the

The Immutable.java example source code

/*
 * ====================================================================
 *
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */
package org.apache.http.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * The class to which this annotation is applied is immutable.  This means that
 * its state cannot be seen to change by callers, which implies that
 * <ul>
 * <li> all public fields are final, 
 * <li> all public final reference fields refer to other immutable objects, and 
 * <li> constructors and methods do not publish references to any internal state
 *      which is potentially mutable by the implementation. </li>
 * </ul>
 * Immutable objects may still have internal mutable state for purposes of performance
 * optimization; some state variables may be lazily computed, so long as they are computed
 * from immutable state and that callers cannot tell the difference.
 * <p>
 * Immutable objects are inherently thread-safe; they may be passed between threads or
 * published without synchronization.
 * <p>
 * Based on code developed by Brian Goetz and Tim Peierls and concepts
 * published in 'Java Concurrency in Practice' by Brian Goetz, Tim Peierls,
 * Joshua Bloch, Joseph Bowbeer, David Holmes and Doug Lea.
 */
@Documented
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.CLASS) // The original version used RUNTIME
public @interface Immutable {
}