Print all of the thread's information and stack traces : Exceptions « Language Basics « Java

Print all of the thread's information and stack traces

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 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.

import java.lang.reflect.Constructor;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

 * General reflection utils

public class ReflectionUtils {

  private static final Class[] emptyArray = new Class[] {};

   * Cache of constructors for each class. Pins the classes so they can't be
   * garbage collected until ReflectionUtils can be collected.
  private static final Map<Class<?>, Constructor<?>> CONSTRUCTOR_CACHE = new ConcurrentHashMap<Class<?>, Constructor<?>>();

  static private ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();

  public static void setContentionTracing(boolean val) {

  private static String getTaskName(long id, String name) {
    if (name == null) {
      return Long.toString(id);
    return id + " (" + name + ")";

   * Print all of the thread's information and stack traces.
   * @param stream
   *          the stream to
   * @param title
   *          a string title for the stack trace
  public static void printThreadInfo(PrintWriter stream, String title) {
    final int STACK_DEPTH = 20;
    boolean contention = threadBean.isThreadContentionMonitoringEnabled();
    long[] threadIds = threadBean.getAllThreadIds();
    stream.println("Process Thread Dump: " + title);
    stream.println(threadIds.length + " active threads");
    for (long tid : threadIds) {
      ThreadInfo info = threadBean.getThreadInfo(tid, STACK_DEPTH);
      if (info == null) {
        stream.println("  Inactive");
      stream.println("Thread " + getTaskName(info.getThreadId(), info.getThreadName()) + ":");
      Thread.State state = info.getThreadState();
      stream.println("  State: " + state);
      stream.println("  Blocked count: " + info.getBlockedCount());
      stream.println("  Waited count: " + info.getWaitedCount());
      if (contention) {
        stream.println("  Blocked time: " + info.getBlockedTime());
        stream.println("  Waited time: " + info.getWaitedTime());
      if (state == Thread.State.WAITING) {
        stream.println("  Waiting on " + info.getLockName());
      } else if (state == Thread.State.BLOCKED) {
        stream.println("  Blocked on " + info.getLockName());
        stream.println("  Blocked by "
            + getTaskName(info.getLockOwnerId(), info.getLockOwnerName()));
      stream.println("  Stack:");
      for (StackTraceElement frame : info.getStackTrace()) {
        stream.println("    " + frame.toString());

  private static long previousLogTime = 0;

   * Return the correctly-typed {@link Class} of the given object.
   * @param o
   *          object whose correctly-typed <code>Class</code> is to be
   *          obtained
   * @return the correctly typed <code>Class</code> of the given object.
  public static <T> Class<T> getClass(T o) {
    return (Class<T>) o.getClass();

  // methods to support testing
  static void clearCache() {

  static int getCacheSize() {
    return CONSTRUCTOR_CACHE.size();



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