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