1 /*
   2  * Copyright (c) 2020, 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 package jdk.test.lib.util;
  25 
  26 import java.lang.ref.Cleaner;
  27 import java.util.concurrent.CountDownLatch;
  28 import java.util.concurrent.TimeUnit;
  29 import java.util.function.BooleanSupplier;
  30 
  31 /**
  32  * Utility class to invoke System.gc()
  33  */
  34 public class ForceGC {
  35     private final CountDownLatch cleanerInvoked = new CountDownLatch(1);
  36     private final Cleaner cleaner = Cleaner.create();
  37     public ForceGC() {
  38         cleaner.register(new Object(), () -> cleanerInvoked.countDown());
  39     }
  40 
  41     private void doit() {
  42         try {
  43             for (int i = 0; i < 10; i++) {
  44                 System.gc();
  45                 System.out.println("gc " + i);
  46                 if (cleanerInvoked.await(1L, TimeUnit.SECONDS)) {
  47                     return;
  48                 }
  49             }
  50         } catch (InterruptedException unexpected) {
  51             throw new AssertionError("unexpected InterruptedException");
  52         }
  53     }
  54 
  55     /**
  56      * Causes the current thread to wait until the {@code BooleanSupplier} returns true,
  57      * unless the thread is interrupted or a predefined waiting time elapses.
  58      *
  59      * @param s boolean supplier
  60      * @return true if the {@code BooleanSupplier} returns true and false if
  61      *         the predefined waiting time elapsed before the count reaches zero.
  62      * @throws InterruptedException if the current thread is interrupted while waiting
  63      */
  64     public boolean await(BooleanSupplier s) {
  65         for (int i = 0; i < 10; i++) {
  66             if (s.getAsBoolean()) return true;
  67             doit();
  68         }
  69         return false;
  70     }
  71 }