编写下面代码，用于演示死锁情况：
public
class ThreadDeadlock {
public static void main(String[]
args) throws InterruptedException {
Object obj1 = new Object();
Object obj2 = new Object();
Object obj3 = new Object();
Thread t1 = new Thread( new SyncThread(obj1,
obj2), "t1");
Thread t2 = new Thread( new SyncThread(obj2,
obj3), "t2");
Thread t3 = new Thread( new SyncThread(obj3,
obj1), "t3");
t1.start();
Thread.sleep(5000);
t2.start();
Thread.sleep(5000);
t3.start();
}
}
class SyncThread implements Runnable
{
private Object obj1;
private Object obj2;
public SyncThread(Object
obj1, Object obj2) {
this. obj1 =
obj1;
this. obj2 =
obj2;
}
@Override
public void run()
{
String name = Thread. currentThread().getName();
System. out.println(name
+ "申请锁:"+obj1 );
synchronized ( obj1)
{
System. out.println(name
+ "获取锁:"+obj1 );
work();
System. out.println(name
+ "申请锁:"+obj2 );
synchronized ( obj2)
{
System. out.println(name
+ "获取锁:"+obj2 );
work();
}
System. out.println(name
+ "释放锁:"+obj2 );
}
System. out.println(name
+ "释放锁:"+obj1 );
System. out.println(name
+ "运行结束");
}
private void work(){
try {
Thread. sleep(30000);
} catch (InterruptedException
e) {
e.printStackTrace();
}
}
}
执行上面的程序时，就产生了输出，但是程序却因为死锁无法停止
t1申请锁:java.lang.Object@1d87b360
t1获取锁:java.lang.Object@1d87b360
t2申请锁:java.lang.Object@47bb2cb
t2获取锁:java.lang.Object@47bb2cb
t3申请锁:java.lang.Object@653e4653
t3获取锁:java.lang.Object@653e4653
t1申请锁:java.lang.Object@47bb2cb
t2申请锁:java.lang.Object@653e4653
t3申请锁:java.lang.Object@1d87b360
要分析线程执行情况，需要用工具 dump 线程信息。可以使用 VisualVM (http://visualvm.java.net/)
运行 VisualVM，直接右键就可以Dump
如果在linux 上 可以用jdk 提供 jstack 工具：
ps -eaf|grep java 找到PID
jstack 26444 >> ~/a.dump
参考文章：
http://www.importnew.com/9668.html
http://www.journaldev.com/1053/how-to-generate-thread-dump-in-java
