1/* 2 * Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 24/* 25 * @test 26 * @bug 6387919 27 * @summary Confirm ThreadLocal.set() usage is not a side effect of get() 28 * @author Pete Soper 29 */ 30public class ImmutableLocal 31{ 32 /** 33 * {@link ThreadLocal} guaranteed to always return the same reference. 34 */ 35 public abstract static class ImmutableThreadLocal extends ThreadLocal { 36 public void set(final Object value) { 37 throw new RuntimeException("ImmutableThreadLocal set called"); 38 } 39 40 // force override 41 protected abstract Object initialValue(); 42 } 43 44 private static final ThreadLocal cache = new ImmutableThreadLocal() { 45 public Object initialValue() { 46 return Thread.currentThread().getName(); 47 } 48 }; 49 50 public static void main(final String[] args) { 51 System.out.println("cache.get() = " + cache.get()); 52 } 53} 54