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Java example source code file (GcFinalizationTest.java)

This example Java source code file (GcFinalizationTest.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

atomicboolean, countdownlatch, finalizationpredicate, gcfinalizationtest, hint, interruptenator, jit, object, override, runnable, runtimeexception, settablefuture, threading, threads, util, weakhashmap, weakreference

The GcFinalizationTest.java Java example source code

/*
 * Copyright (C) 2011 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.testing;

import static com.google.common.truth.Truth.assertThat;

import com.google.common.testing.GcFinalization.FinalizationPredicate;
import com.google.common.util.concurrent.SettableFuture;

import junit.framework.TestCase;

import java.lang.ref.WeakReference;
import java.util.WeakHashMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * Tests for {@link GcFinalization}.
 *
 * @author Martin Buchholz
 * @author mike nonemacher
 */

public class GcFinalizationTest extends TestCase {

  //----------------------------------------------------------------
  // Ordinary tests of successful method execution
  //----------------------------------------------------------------

  public void testAwait_CountDownLatch() {
    final CountDownLatch latch = new CountDownLatch(1);
    Object x = new Object() {
      @Override protected void finalize() { latch.countDown(); }
    };
    x = null;  // Hint to the JIT that x is unreachable
    GcFinalization.await(latch);
    assertEquals(0, latch.getCount());
  }

  public void testAwaitDone_Future() {
    final SettableFuture<Void> future = SettableFuture.create();
    Object x = new Object() {
      @Override protected void finalize() { future.set(null); }
    };
    x = null;  // Hint to the JIT that x is unreachable
    GcFinalization.awaitDone(future);
    assertTrue(future.isDone());
    assertFalse(future.isCancelled());
  }

  public void testAwaitDone_Future_Cancel() {
    final SettableFuture<Void> future = SettableFuture.create();
    Object x = new Object() {
      @Override protected void finalize() { future.cancel(false); }
    };
    x = null;  // Hint to the JIT that x is unreachable
    GcFinalization.awaitDone(future);
    assertTrue(future.isDone());
    assertTrue(future.isCancelled());
  }

  public void testAwaitClear() {
    final WeakReference<Object> ref = new WeakReference(new Object());
    GcFinalization.awaitClear(ref);
    assertNull(ref.get());
  }

  public void testAwaitDone_FinalizationPredicate() {
    final WeakHashMap<Object, Object> map = new WeakHashMap();
    map.put(new Object(), Boolean.TRUE);
    GcFinalization.awaitDone(new FinalizationPredicate() {
      public boolean isDone() {
        return map.isEmpty();
      }
    });
    assertTrue(map.isEmpty());
  }

  //----------------------------------------------------------------
  // Test that interrupts result in RuntimeException, not InterruptedException.
  // Trickier than it looks, because runFinalization swallows interrupts.
  //----------------------------------------------------------------

  class Interruptenator extends Thread {
    final AtomicBoolean shutdown;
    Interruptenator(final Thread interruptee) {
      this(interruptee, new AtomicBoolean(false));
    }
    Interruptenator(final Thread interruptee,
                    final AtomicBoolean shutdown) {
      super(new Runnable() {
          public void run() {
            while (!shutdown.get()) {
              interruptee.interrupt();
              Thread.yield();
            }}});
      this.shutdown = shutdown;
      start();
    }
    void shutdown() {
      shutdown.set(true);
      while (this.isAlive()) {
        Thread.yield();
      }
    }
  }

  void assertWrapsInterruptedException(RuntimeException e) {
    assertThat(e.getMessage()).contains("Unexpected interrupt");
    assertThat(e.getCause()).isInstanceOf(InterruptedException.class);
  }

  public void testAwait_CountDownLatch_Interrupted() {
    Interruptenator interruptenator = new Interruptenator(Thread.currentThread());
    try {
      final CountDownLatch latch = new CountDownLatch(1);
      try {
        GcFinalization.await(latch);
        fail("should throw");
      } catch (RuntimeException expected) {
        assertWrapsInterruptedException(expected);
      }
    } finally {
      interruptenator.shutdown();
      Thread.interrupted();
    }
  }

  public void testAwaitDone_Future_Interrupted_Interrupted() {
    Interruptenator interruptenator = new Interruptenator(Thread.currentThread());
    try {
      final SettableFuture<Void> future = SettableFuture.create();
      try {
        GcFinalization.awaitDone(future);
        fail("should throw");
      } catch (RuntimeException expected) {
        assertWrapsInterruptedException(expected);
      }
    } finally {
      interruptenator.shutdown();
      Thread.interrupted();
    }
  }

  public void testAwaitClear_Interrupted() {
    Interruptenator interruptenator = new Interruptenator(Thread.currentThread());
    try {
      final WeakReference<Object> ref = new WeakReference(Boolean.TRUE);
      try {
        GcFinalization.awaitClear(ref);
        fail("should throw");
      } catch (RuntimeException expected) {
        assertWrapsInterruptedException(expected);
      }
    } finally {
      interruptenator.shutdown();
      Thread.interrupted();
    }
  }

  public void testAwaitDone_FinalizationPredicate_Interrupted() {
    Interruptenator interruptenator = new Interruptenator(Thread.currentThread());
    try {
      try {
        GcFinalization.awaitDone(new FinalizationPredicate() {
            public boolean isDone() {
              return false;
            }
          });
        fail("should throw");
      } catch (RuntimeException expected) {
        assertWrapsInterruptedException(expected);
      }
    } finally {
      interruptenator.shutdown();
      Thread.interrupted();
    }
  }

  /**
   * awaitFullGc() is not quite as reliable a way to ensure calling of a
   * specific finalize method as the more direct await* methods, but should be
   * reliable enough in practice to avoid flakiness of this test.  (And if it
   * isn't, we'd like to know about it first!)
   */
  public void testAwaitFullGc() {
    final CountDownLatch finalizerRan = new CountDownLatch(1);
    final WeakReference<Object> ref = new WeakReference(
        new Object() {
          @Override protected void finalize() { finalizerRan.countDown(); }
        });

    // Don't copy this into your own test!
    // Use e.g. awaitClear or await(CountDownLatch) instead.
    GcFinalization.awaitFullGc();

    // If this test turns out to be flaky, add a second call to awaitFullGc()
    // GcFinalization.awaitFullGc();

    assertEquals(0, finalizerRan.getCount());
    assertNull(ref.get());
  }

}




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