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Java 多线程编程之四：获取 Java VM 中当前运行的所有线程

分类: 文章 • 2025-07-08 19:16:28

获取 Java VM 中当前运行的所有线程

程序运行图：

Java 多线程编程之四：获取 Java VM 中当前运行的所有线程
下面的静态方法可以用数组返回 Java VM 中当前运行的所有线程
public static Thread[] findAllThreads() {
ThreadGroup group =
Thread.currentThread().getThreadGroup();
ThreadGroup topGroup = group;

// 遍历线程组树，获取根线程组
while ( group != null ) {
topGroup = group;
group = group.getParent();
}
// **的线程数加倍
int estimatedSize = topGroup.activeCount() * 2;
Thread[] slackList = new Thread[estimatedSize];
//获取根线程组的所有线程
int actualSize = topGroup.enumerate(slackList);
// copy into a list that is the exact size
Thread[] list = new Thread[actualSize];
System.arraycopy(slackList, 0, list, 0, actualSize);
return list;
}

程序 ThreadViewer.java 以图形方式显示 Java VM 中当前运行的所有线程,它每隔 2 秒自动刷新一次,以保持获得最新信息。程序 ThreadViewer.java 源代码：

[java]view plaincopyprint?
  1. packagethread;
  2. importjava.awt.*;
  3. importjava.awt.event.*;
  4. importjavax.swing.*;
  5. importjavax.swing.table.*;
  6. publicclassThreadViewerextendsJPanel{
  7. privateThreadViewerTableModeltableModel;
  8. publicThreadViewer(){
  9. tableModel=newThreadViewerTableModel();
  10. JTabletable=newJTable(tableModel);
  11. table.setAutoResizeMode(JTable.AUTO_RESIZE_LAST_COLUMN);
  12. TableColumnModelcolModel=table.getColumnModel();
  13. intnumColumns=colModel.getColumnCount();
  14. //manuallysizeallbutthelastcolumn
  15. for(inti=0;i<numColumns-1;i++){
  16. TableColumncol=colModel.getColumn(i);
  17. col.sizeWidthToFit();
  18. col.setPreferredWidth(col.getWidth()+5);
  19. col.setMaxWidth(col.getWidth()+5);
  20. }
  21. JScrollPanesp=newJScrollPane(table);
  22. setLayout(newBorderLayout());
  23. add(sp,BorderLayout.CENTER);
  24. }
  25. publicvoiddispose(){
  26. tableModel.stopRequest();
  27. }
  28. protectedvoidfinalize()throwsThrowable{
  29. dispose();
  30. }
  31. publicstaticJFramecreateFramedInstance(){
  32. finalThreadViewerviewer=newThreadViewer();
  33. finalJFramef=newJFrame("ThreadViewer");
  34. f.addWindowListener(newWindowAdapter(){
  35. publicvoidwindowClosing(WindowEvente){
  36. f.setVisible(false);
  37. f.dispose();
  38. viewer.dispose();
  39. }
  40. });
  41. f.setContentPane(viewer);
  42. f.setSize(500,300);
  43. f.setVisible(true);
  44. returnf;
  45. }
  47. publicstaticvoidmain(String[]args){
  48. JFramef=ThreadViewer.createFramedInstance();
  49. //Forthisexample,exittheVMwhentheviewer
  50. //frameisclosed.
  51. f.addWindowListener(newWindowAdapter(){
  52. publicvoidwindowClosing(WindowEvente){
  53. System.exit(0);
  54. }
  55. });
  56. //Keepthemainthreadfromexitingbyblocking
  57. //onwait()foranotificationthatnevercomes.
  58. Objectlock=newObject();
  59. synchronized(lock){
  60. try{
  61. lock.wait();
  62. }catch(InterruptedExceptionx){
  63. }
  64. }
  65. }
  66. }

程序 ThreadViewerTableModel.java 源代码：

[java]view plaincopyprint?
  1. packagethread;
  2. importjava.awt.*;
  3. importjava.lang.reflect.*;
  4. importjavax.swing.*;
  5. importjavax.swing.table.*;
  6. publicclassThreadViewerTableModelextendsAbstractTableModel{
  7. privateObjectdataLock;
  8. privateintrowCount;
  9. privateObject[][]cellData;
  10. privateObject[][]pendingCellData;
  11. //thecolumninformationremainsconstant
  12. privatefinalintcolumnCount;
  13. privatefinalString[]columnName;
  14. privatefinalClass[]columnClass;
  15. //self-runningobjectcontrolvariables
  16. privateThreadinternalThread;
  17. privatevolatilebooleannoStopRequested;
  18. publicThreadViewerTableModel(){
  19. rowCount=0;
  20. cellData=newObject[0][0];
  21. //JTableusesthisinformationforthecolumnheaders
  22. String[]names={
  23. "Priority","Alive",
  24. "Daemon","Interrupted",
  25. "ThreadGroup","ThreadName"};
  26. columnName=names;
  28. //JTableusesthisinformationforcellrendering
  29. Class[]classes={
  30. Integer.class,Boolean.class,
  31. Boolean.class,Boolean.class,
  32. String.class,String.class};
  33. columnClass=classes;
  34. columnCount=columnName.length;
  35. //usedtocontrolconcurrentaccess
  36. dataLock=newObject();
  37. noStopRequested=true;
  38. Runnabler=newRunnable(){
  39. publicvoidrun(){
  40. try{
  41. runWork();
  42. }catch(Exceptionx){
  43. //incaseANYexceptionslipsthrough
  44. x.printStackTrace();
  45. }
  46. }
  47. };
  48. internalThread=newThread(r,"ThreadViewer");
  49. internalThread.setPriority(Thread.MAX_PRIORITY-2);
  50. internalThread.setDaemon(true);
  51. internalThread.start();
  52. }
  53. privatevoidrunWork(){
  54. //Therun()methodoftransferPendingiscalledby
  55. //theeventhandlingthreadforsafeconcurrency.
  56. RunnabletransferPending=newRunnable(){
  57. publicvoidrun(){
  58. transferPendingCellData();
  59. //MethodofAbstractTableModelthat
  60. //causesthetabletobeupdated.
  61. fireTableDataChanged();
  62. }
  63. };
  64. while(noStopRequested){
  65. try{
  66. createPendingCellData();
  67. SwingUtilities.invokeAndWait(transferPending);
  68. Thread.sleep(2000);
  69. }catch(InvocationTargetExceptiontx){
  70. tx.printStackTrace();
  71. stopRequest();
  72. }catch(InterruptedExceptionx){
  73. Thread.currentThread().interrupt();
  74. }
  75. }
  76. }
  77. publicvoidstopRequest(){
  78. noStopRequested=false;
  79. internalThread.interrupt();
  80. }
  81. publicbooleanisAlive(){
  82. returninternalThread.isAlive();
  83. }
  84. privatevoidcreatePendingCellData(){
  85. //thismethodiscalledbytheinternalthread
  86. Thread[]thread=findAllThreads();
  87. Object[][]cell=newObject[thread.length][columnCount];
  88. for(inti=0;i<thread.length;i++){
  89. Threadt=thread[i];
  90. Object[]rowCell=cell[i];
  91. rowCell[0]=newInteger(t.getPriority());
  92. rowCell[1]=newBoolean(t.isAlive());
  93. rowCell[2]=newBoolean(t.isDaemon());
  94. rowCell[3]=newBoolean(t.isInterrupted());
  95. rowCell[4]=t.getThreadGroup().getName();
  96. rowCell[5]=t.getName();
  97. }
  98. synchronized(dataLock){
  99. pendingCellData=cell;
  100. }
  101. }
  102. privatevoidtransferPendingCellData(){
  103. //thismethodiscalledbytheeventthread
  104. synchronized(dataLock){
  105. cellData=pendingCellData;
  106. rowCount=cellData.length;
  107. }
  108. }
  109. publicintgetRowCount(){
  110. //thismethodiscalledbytheeventthread
  111. returnrowCount;
  112. }
  114. publicObjectgetValueAt(introw,intcol){
  115. //thismethodiscalledbytheeventthread
  116. returncellData[row][col];
  117. }
  118. publicintgetColumnCount(){
  119. returncolumnCount;
  120. }
  121. publicClassgetColumnClass(intcolumnIdx){
  122. returncolumnClass[columnIdx];
  123. }
  124. publicStringgetColumnName(intcolumnIdx){
  125. returncolumnName[columnIdx];
  126. }
  127. publicstaticThread[]findAllThreads(){
  128. ThreadGroupgroup=
  129. Thread.currentThread().getThreadGroup();
  130. ThreadGrouptopGroup=group;
  131. //traversetheThreadGrouptreetothetop
  132. while(group!=null){
  133. topGroup=group;
  134. group=group.getParent();
  135. }
  136. //Createadestinationarraythatisabout
  137. //twiceasbigasneededtobeveryconfident
  138. //thatnoneareclipped.
  139. intestimatedSize=topGroup.activeCount()*2;
  140. Thread[]slackList=newThread[estimatedSize];
  141. //Loadthethreadreferencesintotheoversized
  142. //array.Theactualnumberofthreadsloaded
  143. //isreturned.
  144. intactualSize=topGroup.enumerate(slackList);
  145. //copyintoalistthatistheexactsize
  146. Thread[]list=newThread[actualSize];
  147. System.arraycopy(slackList,0,list,0,actualSize);
  148. returnlist;
  149. }
  150. }

http://blog.****.net/defonds/article/details/4848853

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