死锁代码。解除 加wait notify即可 

package nowcode.test;

public class DeadLock {
    public static void main(String[] args) throws InterruptedException {
        final DeadLock dd1 = new DeadLock();
        final DeadLock dd2 = new DeadLock();

        Thread t1 = new Thread(new Runnable() {
            public void run() {
                //首先获得dd1的锁
                synchronized (dd1) {
                    //休眠
                    try {
                        Thread.sleep(50);
                        synchronized (dd2) {
                            System.out.println(Thread.currentThread().getName() + "线程。。");
                           // dd2.notify();
                        }
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
        }, "t1");

        Thread t2 = new Thread(new Runnable() {
            public void run() {
                synchronized (dd2) {
                    try {
                      // dd2.wait();
                        Thread.sleep(50);
                        synchronized (dd1) {
                            System.out.println(Thread.currentThread().getName() + "线程。。");
                        }
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
        }, "t2");
        t1.start();
        t2.start();
    }

}

jps -l定位线程

jstack -l 线程数 定位分析

或者