java线程状态——死锁

参考：

java 线程状态

java 线程状态——情况续说

java线程状态——java线程状态图

死锁，概念有很多，可以google

现在列出死锁的模拟代码和jstack的输出

一方面是理解死锁，一方面是学习jstack找出死锁，进行代码调优

import java.util.concurrent.TimeUnit;public class e{        static class DeadT implements Runnable        {                private Object lock1;                private Object lock2;                private String name;                private String lockname1;                private String lockname2;                public DeadT(Object lock1,Object lock2,String name,String lockname1,String lockname2)                {                        this.lock1 = lock1;                        this.lock2 = lock2;                        this.name = name;                        this.lockname1 = lockname1;                        this.lockname2 = lockname2;                }                public void run()                {                        System.out.println(name+" acquiring lock"+lockname1+"... ");                        synchronized(lock1)                        {                                System.out.println(name + " acquired lock"+lockname1+"... ");                                work();                                System.out.println(name + " acquiring lock"+lockname2+"... ");                                synchronized(lock2)                                {                                        System.out.println(name + " acquired lock"+lockname2+"... ");                                }                        }                }//end run                public void work()                {                        try                        {                                TimeUnit.SECONDS.sleep(8);                        } catch(Exception e)                        {                                e.printStackTrace();                        }                }        }        public static void main(String[] args)        {                Object lock1 = new Object();                Object lock2 = new Object();                Thread t1 = new Thread(new DeadT(lock1,lock2,"t1","1","2"));                Thread t2 = new Thread(new DeadT(lock2,lock1,"t2","2","1"));                t1.setName("t1");                t2.setName("t2");                t1.start();                try                {                        TimeUnit.SECONDS.sleep(2);                }                catch(Exception e)                {                        e.printStackTrace();                }                t2.start();                try                {                        TimeUnit.SECONDS.sleep(2);                }                catch(Exception e)                {                        e.printStackTrace();                }                System.out.println("main finished!");        }

jstack输出如下：

2017-02-14 14:13:20Full thread dump Java HotSpot(TM) 64-Bit Server VM (24.80-b11 mixed mode):   java.lang.Thread.State: RUNNABLE"DestroyJavaVM" prio=10 tid=0x00007f8c68008800 nid=0x37a4 waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"t2" prio=10 tid=0x00007f8c680bb000 nid=0x37b6 waiting for monitor entry [0x00007f8c55cd4000]   java.lang.Thread.State: BLOCKED (on object monitor)        at e$DeadT.run(e.java:33)        - waiting to lock <0x00000007d704aa10> (a java.lang.Object)        - locked <0x00000007d704aa20> (a java.lang.Object)        at java.lang.Thread.run(Thread.java:745)"t1" prio=10 tid=0x00007f8c680b9000 nid=0x37b5 waiting for monitor entry [0x00007f8c55dd5000]   java.lang.Thread.State: BLOCKED (on object monitor)        at e$DeadT.run(e.java:33)        - waiting to lock <0x00000007d704aa20> (a java.lang.Object)        - locked <0x00000007d704aa10> (a java.lang.Object)        at java.lang.Thread.run(Thread.java:745)   java.lang.Thread.State: RUNNABLE   java.lang.Thread.State: RUNNABLE   java.lang.Thread.State: RUNNABLE   java.lang.Thread.State: RUNNABLE   java.lang.Thread.State: WAITING (on object monitor)        at java.lang.Object.wait(Native Method)        - waiting on <0x00000007d7004858> (a java.lang.ref.ReferenceQueue$Lock)        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)        - locked <0x00000007d7004858> (a java.lang.ref.ReferenceQueue$Lock)        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)        at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)   java.lang.Thread.State: WAITING (on object monitor)        at java.lang.Object.wait(Native Method)        - waiting on <0x00000007d7004470> (a java.lang.ref.Reference$Lock)        at java.lang.Object.wait(Object.java:503)        at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:133)        - locked <0x00000007d7004470> (a java.lang.ref.Reference$Lock)"GC task thread#0 (ParallelGC)" prio=10 tid=0x00007f8c6801e000 nid=0x37a5 runnable"GC task thread#1 (ParallelGC)" prio=10 tid=0x00007f8c68020000 nid=0x37a6 runnable"GC task thread#2 (ParallelGC)" prio=10 tid=0x00007f8c68022000 nid=0x37a7 runnable"GC task thread#3 (ParallelGC)" prio=10 tid=0x00007f8c68023800 nid=0x37a8 runnable"GC task thread#4 (ParallelGC)" prio=10 tid=0x00007f8c68025800 nid=0x37a9 runnable"GC task thread#5 (ParallelGC)" prio=10 tid=0x00007f8c68027800 nid=0x37aa runnable"GC task thread#6 (ParallelGC)" prio=10 tid=0x00007f8c68029000 nid=0x37ab runnable"GC task thread#7 (ParallelGC)" prio=10 tid=0x00007f8c6802b000 nid=0x37ac runnable"VM Periodic Task Thread" prio=10 tid=0x00007f8c680aa000 nid=0x37b4 waiting on conditionJNI global references: 107Found one Java-level deadlock:============================="t2":  waiting to lock monitor 0x00007f8c1c006218 (object 0x00000007d704aa10, a java.lang.Object),  which is held by "t1""t1":  waiting to lock monitor 0x00007f8c1c003988 (object 0x00000007d704aa20, a java.lang.Object),  which is held by "t2"Java stack information for the threads listed above:==================================================="t2":        at e$DeadT.run(e.java:33)        - waiting to lock <0x00000007d704aa10> (a java.lang.Object)        - locked <0x00000007d704aa20> (a java.lang.Object)        at java.lang.Thread.run(Thread.java:745)"t1":        at e$DeadT.run(e.java:33)        - waiting to lock <0x00000007d704aa20> (a java.lang.Object)        - locked <0x00000007d704aa10> (a java.lang.Object)        at java.lang.Thread.run(Thread.java:745)Found 1 deadlock.

从jstack输出中可以很明显找到deadlock的字眼，并在最后说出了死锁的条件，请仔细看jstack输出以及代码。