引言
这个情况现象的程序运行的时候迟迟没有输出，我们可以怀疑的死锁的问题，但是怎么去定位这个问题呢，我们还是借助jstack来做。
jstack 163746
这个查看没有太复杂的流程，直接查看堆栈信息最后的一部分就ok
Found one Java-level deadlock: ============================= "Thread_02": waiting to lock monitor 0x00002b578c002178 (object 0x000000058015e5c0, a O1), which is held by "Thread_01" "Thread_01": waiting to lock monitor 0x00002b578c006218 (object 0x000000058015f148, a O2), which is held by "Thread_02" Java stack information for the threads listed above: =================================================== "Thread_02": at Demo1_3.lambda$main$1(Demo1_3.java:28) - waiting to lock <0x000000058015e5c0> (a O1) - locked <0x000000058015f148> (a O2) at Demo1_3$$Lambda$2/1418481495.run(Unknown Source) at java.lang.Thread.run(Thread.java:745) "Thread_01": at Demo1_3.lambda$main$0(Demo1_3.java:17) - waiting to lock <0x000000058015f148> (a O2) - locked <0x000000058015e5c0> (a O1) at Demo1_3$$Lambda$1/834600351.run(Unknown Source) at java.lang.Thread.run(Thread.java:745) Found 1 deadlock.
信息会很明确告诉有一个死锁，并且指明了代码行17行和28行，定位到这里就方便了，我们拿出源代码看看：
class O1{} class O2{} public class Demo1_3 { static O1 o1=new O1(); static O2 o2=new O2(); public static void main(String[] args) throws InterruptedException { new Thread(()->{ synchronized (o1){ try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } synchronized (o2){ System.out.println("我是线程1，我获得了o1和o2"); } } },"Thread_01").start(); Thread.sleep(1000); new Thread(()->{ synchronized (o2){ synchronized (o1){ System.out.println("我是线程2,我获得了o1和o2"); } } },"Thread_02").start(); } }
可以看到，线程1和2分别取锁定o1和o2，线程1在持有了o1的同时又准备去锁住o2，而线程2则先持有o2再去锁定o1,双方都没有释放，进而死锁了。
