/*

 * Copyright (c) 2013, 2018, 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 KeepAliveSoftReference

 * @summary This test case uses a java.lang.ref.SoftReference referencing a class instance to keep a class alive.

 * @requires vm.opt.final.ClassUnloading

 * @modules java.base/jdk.internal.misc

 * @library /test/lib /runtime/testlibrary

 * @library classes

 * @build sun.hotspot.WhiteBox test.Empty

 * @run driver ClassFileInstaller sun.hotspot.WhiteBox

 *                              sun.hotspot.WhiteBox$WhiteBoxPermission

 * @run main/othervm -Xbootclasspath/a:. -Xmn8m -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI KeepAliveSoftReference

 */

import java.lang.ref.SoftReference;

import sun.hotspot.WhiteBox;

/**

 * Test that verifies that classes are not unloaded when specific types of references are kept to them.

 */

public class KeepAliveSoftReference {

  private static final String className = "test.Empty";

  private static final WhiteBox wb = WhiteBox.getWhiteBox();

  public static void main(String... args) throws Exception {

    ClassLoader cl = ClassUnloadCommon.newClassLoader();

    Class<?> c = cl.loadClass(className);

    Object o = c.newInstance();

    SoftReference<Object> sr = new SoftReference(o);

    o = null; c = null; cl = null;

    {

        boolean isAlive = wb.isClassAlive(className);

        System.out.println("testSoftReference (1) alive: " + isAlive);

        boolean cleared = (sr.get() == null);

        boolean shouldBeAlive = !cleared;

        ClassUnloadCommon.failIf(isAlive != shouldBeAlive, "" + isAlive + " != " + shouldBeAlive);

    }

    ClassUnloadCommon.triggerUnloading();

    {

        boolean isAlive = wb.isClassAlive(className);

        System.out.println("testSoftReference (2) alive: " + isAlive);

        boolean cleared = (sr.get() == null);

        boolean shouldBeAlive = !cleared;

        ClassUnloadCommon.failIf(isAlive != shouldBeAlive, "" + isAlive + " != " + shouldBeAlive);

    }

    sr.clear();

    ClassUnloadCommon.triggerUnloading();

    {

        boolean isAlive = wb.isClassAlive(className);

        System.out.println("testSoftReference (3) alive: " + isAlive);

        boolean cleared = (sr.get() == null);

        boolean shouldBeAlive = !cleared;

        ClassUnloadCommon.failIf(isAlive != shouldBeAlive, "" + isAlive + " != " + shouldBeAlive);

    }

  }

}