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Java example source code file (Thread.java)

This example Java source code file (Thread.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

address, addressfield, cintegerfield, ext_suspended, external_suspend, has_async_exception, jnihandleblock, objectmonitor, thread, thread\:\:_ext_suspended, thread\:\:_external_suspend, thread\:\:_has_async_exception, threadlocalallocbuffer, type, util

The Thread.java Java example source code

/*
 * Copyright (c) 2000, 2011, 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.
 *
 */

package sun.jvm.hotspot.runtime;

import java.util.*;
import sun.jvm.hotspot.debugger.*;
import sun.jvm.hotspot.types.*;

public class Thread extends VMObject {
  private static long tlabFieldOffset;

  private static CIntegerField suspendFlagsField;
  // Thread::SuspendFlags enum constants
  private static int EXTERNAL_SUSPEND;
  private static int EXT_SUSPENDED;
  private static int HAS_ASYNC_EXCEPTION;

  private static AddressField activeHandlesField;
  private static AddressField currentPendingMonitorField;
  private static AddressField currentWaitingMonitorField;

  static {
    VM.registerVMInitializedObserver(new Observer() {
        public void update(Observable o, Object data) {
          initialize(VM.getVM().getTypeDataBase());
        }
      });
  }

  private static synchronized void initialize(TypeDataBase db) {
    Type type = db.lookupType("Thread");

    suspendFlagsField = type.getCIntegerField("_suspend_flags");
    EXTERNAL_SUSPEND = db.lookupIntConstant("Thread::_external_suspend").intValue();
    EXT_SUSPENDED = db.lookupIntConstant("Thread::_ext_suspended").intValue();
    HAS_ASYNC_EXCEPTION = db.lookupIntConstant("Thread::_has_async_exception").intValue();

    tlabFieldOffset    = type.getField("_tlab").getOffset();
    activeHandlesField = type.getAddressField("_active_handles");
    currentPendingMonitorField = type.getAddressField("_current_pending_monitor");
    currentWaitingMonitorField = type.getAddressField("_current_waiting_monitor");
  }

  public Thread(Address addr) {
    super(addr);
  }

  public int suspendFlags() {
    return (int) suspendFlagsField.getValue(addr);
  }

  public boolean isExternalSuspend() {
    return (suspendFlags() & EXTERNAL_SUSPEND) != 0;
  }

  public boolean isExtSuspended() {
    return (suspendFlags() & EXT_SUSPENDED) != 0;
  }

  public boolean isBeingExtSuspended() {
    return isExtSuspended() || isExternalSuspend();
  }

  // historical usage: checked for VM or external suspension
  public boolean isAnySuspended() {
    return isExtSuspended();
  }

  public boolean hasAsyncException() {
    return (suspendFlags() & HAS_ASYNC_EXCEPTION) != 0;
  }

  public ThreadLocalAllocBuffer tlab() {
    return new ThreadLocalAllocBuffer(addr.addOffsetTo(tlabFieldOffset));
  }

  public JNIHandleBlock activeHandles() {
    Address a = activeHandlesField.getAddress(addr);
    if (a == null) {
      return null;
    }
    return new JNIHandleBlock(a);
  }

  public boolean   isVMThread()                { return false; }
  public boolean   isJavaThread()              { return false; }
  public boolean   isCompilerThread()          { return false; }
  public boolean   isHiddenFromExternalView()  { return false; }
  public boolean   isJvmtiAgentThread()        { return false; }
  public boolean   isWatcherThread()           { return false; }
  public boolean   isConcurrentMarkSweepThread() { return false; }
  public boolean   isServiceThread()           { return false; }

  /** Memory operations */
  public void oopsDo(AddressVisitor oopVisitor) {
    // FIXME: Empty for now; will later traverse JNI handles and
    // pending exception
  }

  public ObjectMonitor getCurrentPendingMonitor() {
    Address monitorAddr = currentPendingMonitorField.getValue(addr);
    if (monitorAddr == null) {
      return null;
    }
    return new ObjectMonitor(monitorAddr);
  }

  public ObjectMonitor getCurrentWaitingMonitor() {
    Address monitorAddr = currentWaitingMonitorField.getValue(addr);
    if (monitorAddr == null) {
      return null;
    }
    return new ObjectMonitor(monitorAddr);
  }

  public boolean isLockOwned(Address lock) {
    if (isInStack(lock)) return true;
    return false;
  }

  public boolean isInStack(Address a) {
    // In the Serviceability Agent we need access to the thread's
    // stack pointer to be able to answer this question. Since it is
    // only a debugging system at the moment we need access to the
    // underlying thread, which is only present for Java threads; see
    // JavaThread.java.
    return false;
  }

  /** Assistance for ObjectMonitor implementation */
  Address threadObjectAddress() { return addr; }
}

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