108 lines
4.0 KiB
Java
108 lines
4.0 KiB
Java
/*
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* Copyright (c) 2002, 2020, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* @test
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*
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* @summary converted from VM Testbase gc/gctests/ClassDeallocGC.
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* VM Testbase keywords: [gc]
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* VM Testbase readme:
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* This test is a slightly modified version of a test taken from a research paper
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* by CE McDowell of UCSC titled 'No so static "static fields"'.
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* To quote from the paper :
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* " In this paper we have identified a problem with the Java Language
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* Specification with regard to class unloading and static fields. We have
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* provided an example that demonstrates how the current implementation of
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* class unloading can result in a static field being reinitialized resulting
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* in a program that changes its behavior depending upon when garbage collection occurs."
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* In this test, the creation of the object first assigned to
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* class_one_object (actually an instance of ClassOne) also creates an instance
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* of ClassTwo which contains a static field. Once the references to the ClassOne
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* object and the Class object are set to null, a call to the garbage
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* collector results in both ClassOne and ClassTwo being unloaded. When
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* the final assignment to class_one_object occurs, creating a new instance of ClassOne
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* and a new instance of ClassTwo, the program should print out the value of counter in
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* ClassTwo as 2. This would mean that class was not unloaded and the static field
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* was not reinitialized. If the test prints out 1, the test has failed as the static
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* field was reinitilized.
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*
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* @library /vmTestbase
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* /test/lib
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* @run main/othervm gc.gctests.ClassDeallocGC.ClassDeallocGC
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*/
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package gc.gctests.ClassDeallocGC;
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import nsk.share.TestFailure;
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public class ClassDeallocGC
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{
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public static void main(String[] args)
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throws java.io.IOException, ClassNotFoundException,
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IllegalAccessException, InstantiationException
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{
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int count = 0, counter;
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ClassOne class_one_object;
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/* load the class ClassOne and instantiate an instance of it */
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/* ClassOne uses ClassTwo which will thus get loaded also */
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Class theClass = Class.forName("gc.gctests.ClassDeallocGC.ClassOne");
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class_one_object = (ClassOne)theClass.newInstance();
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/* remove all references to the class and the instance */
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class_one_object = null;
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theClass = null;
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System.gc(); /* force garbage collection which also unloads classes */
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/*loads and instantiates ClassOne again. ClassTwo also gets reloaded*/
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class_one_object = (ClassOne) new ClassOne();
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if ( (counter = class_one_object.getCounter()) == 2 ) {
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System.out.println("Test Passed.");
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} else {
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throw new TestFailure("Test failed. counter = " + counter + ", should be 2.");
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}
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}
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}
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class ClassOne {
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ClassTwo class_two;
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public ClassOne(){
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class_two = new ClassTwo();
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}
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public int getCounter() {
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return class_two.getCounter();
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}
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}
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class ClassTwo {
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static int counter = 0;
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public ClassTwo(){
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counter++;
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}
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public int getCounter() {
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return counter;
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}
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}
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