Thread locks

[Changchun Wang]

there are a synchronized static method and a synchronized instance method
in one class
just like this
Demo implements Runnable
{
public synchronized static void get(){
int i=0;
while (i++<100){System.out.println("static");}}
public synchronized void set(){
int i=0;
while (i++<100)
{
System.out.println("static");}
}
public void run(){}

}
I want to know if one thread invoke the get()method while another thread invoke the set() method


I have already Tested it
public Demo
{
public void main(String ...args)
final Test t=new Test();
new Thread(t){public void run(){get()}}.start();
new Thread(t){public void run(){set()}}.start();
}

but I can get the answer?
who can explain it to me ?
thanks

[Mark Spritzler]

I'd say, that even though your test runs two threads, you can't guarantee that they are actually running at exactly the same time.

Mark

[Changchun Wang]

maybe I will ask this question by another way?
we know there exists Object lock and class lock
when frist thread invoke a synchronized instance method,second thread which also will invoke another synchronized instance method from same class need to wait and execute until the frist thread released object lock

but when frist thread invoke a synchronized static method,second thread which also will invoke a synchronized instance method from same class if need to wait and execute until the frist thread released class lock or not

who can explain it to me?
thanks
[ March 31, 2006: Message edited by: Changchun Wang ]

[Henry Wong]

When a synchronized method is called, it will try to grab the lock. If it is owned by another thread, it will wait.

A synchronized static method will use the lock of the Class object representing the class. A synchronized (instance) method, will use the object instance as the lock. These are *two* different locks, hence, calling a synchronized static method, and synchronized method, will be executed in parallel.

Henry

[Changchun Wang]

Originally posted by Henry Wong:

A synchronized static method will use the lock of the Class object representing the class. A synchronized (instance) method, will use the object instance as the lock. These are *two* different locks, hence, calling a synchronized static method, and synchronized method, will be executed in parallel.

Henry

I think both synchronized (static) mehod and synchronized (instance) mehod can access static field
we know introduce synchronized this key word is to solve Sharing and exclusive problems in the thread
but if that two method which executed in parallel will result in above prblems (Sharing and exclusive problems)?
thanks !