java - Why does the synchronized lock another method? -

i'm new multiple-thread in java.i write class test functions of synchronized.i have method using synchronized:

    public class shareutil {         private static queue<integer> queue = new linkedlist<integer>();         public static synchronized void do1(){             system.out.println("do1");             sleep();         }         public static synchronized void do2(){             system.out.println("do2");             sleep();         }         private static void sleep(){             try {                 thread.sleep(1000*50000);             } catch (interruptedexception e) {                 // todo auto-generated catch block                 e.printstacktrace();             }         } } 

you can see there 2 method using synchronized,and run 2 thread use these 2 methods respectively.

class run1 implements runnable{      @override     public void run() {         // todo auto-generated method stub         shareutil.do1();     }  } class run2 implements runnable{      @override     public void run() {         // todo auto-generated method stub         shareutil.do2();     }  } public class domain {     public static void main(string[] args) {         executorservice pools = executors.newcachedthreadpool();         for(int i=0;i<10;i++){             pools.execute(new run1());             pools.execute(new run2());         }         pools.shutdown();     } } 

but,it print "do1" not print "do2".i want know why?the key of "synchronized" using method make method 1 thread use @ same time,but why lock others method?

the important key synchronized locks object, not method.

according https://docs.oracle.com/javase/tutorial/essential/concurrency/locksync.html

every object has intrinsic lock associated it. convention, thread needs exclusive , consistent access object's fields has acquire object's intrinsic lock before accessing them, , release intrinsic lock when it's done them. thread said own intrinsic lock between time has acquired lock , released lock. as long thread owns intrinsic lock, no other thread can acquire same lock. other thread block when attempts acquire lock.

so, shareutil 's class intrinsic lock(your method static, intrinsic lock class object associated class) is locked when thread t1 doing do1(), no other thread can acquire lock unless t1 release it.

and method sleep() call not release lock , while if call wait() , check difference between wait() , sleep(). is reason why when thread t2 try access do2(), must wait t1's do1() complete(intrinsic lock released).