jps

在命令行输入 jps

就会显示所有java线程的信息主要是 pid（进程控制符）

jps(Java Virtual Machine Process Status Tool)

可以结合jstack 打印出某一时刻的堆栈信息

比如检查死锁：


public class DeadLockDemo {

    /** A锁 */
    private static String A = "A";
    /** B锁 */
    private static String B = "B";

    public static void main(String[] args) {
        new DeadLockDemo().deadLock();
    }

    private void deadLock() {
        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                synchronized (A) {
                    try {
                        Thread.sleep(2000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    synchronized (B) {
                        System.out.println("1");
                    }
                }
            }
        });

        Thread t2 = new Thread(new Runnable() {
            @Override
            public void run() {
                synchronized (B) {
                    synchronized (A) {
                        System.out.println("2");
                    }
                }
            }
        });
        t1.start();
        t2.start();
    }

}

运行这一段程序，在命令行输入 jps

找到线程的pid为27976，再输入： jstack 27976

就会有一大堆信息

Found one Java-level deadlock:
=============================
“Thread-1”:
waiting to lock monitor 0x0000000019931368 (object 0x0000000780cbc5b0, a java.lang.String),
which is held by “Thread-0”
“Thread-0”:
waiting to lock monitor 0x0000000019932808 (object 0x0000000780cbc5e0, a java.lang.String),
which is held by “Thread-1”

Java stack information for the threads listed above:
===================================================
“Thread-1”:
        at chapter01.DeadLockDemo$2.run(DeadLockDemo.java:42)
        – waiting to lock <0x0000000780cbc5b0> (a java.lang.String)
        – locked <0x0000000780cbc5e0> (a java.lang.String)
        at java.lang.Thread.run(Thread.java:748)
“Thread-0”:
        at chapter01.DeadLockDemo$1.run(DeadLockDemo.java:31)
        – waiting to lock <0x0000000780cbc5e0> (a java.lang.String)
        – locked <0x0000000780cbc5b0> (a java.lang.String)
        at java.lang.Thread.run(Thread.java:748)

Found 1 deadlock.