Android Multithreading Research (3) thread synchronization and mutex and deadlock

Why is the concept of thread synchronization? Why sync? What is thread synchronization? First look at a piece of code:

Package com.maso.test;  
          
    public class ThreadTest2 implements runnable{private testobj testobj = new Testobj ();  
        public static void Main (string[] args) {ThreadTest2 tt = new ThreadTest2 ();  
        thread T1 = new Thread (TT, "thread_1");  
        Thread t2 = new Thread (TT, "thread_2");  
        T1.start ();  
    T2.start (); @Override public void Run () {for (int j = 0; J < J + +) {in  
            t i = fix (1);  
            try {thread.sleep (1);  
            catch (Interruptedexception e) {e.printstacktrace ();  
        } System.out.println (Thread.CurrentThread (). GetName () + ": i =" + i);  
    ' public int ' fix (int y) {return testobj.fix (y);  
              
        public class testobj{int x = 10; public int fix (intY) {return x = x-y; }  
    }  
          
          
}

When you output the result, you will find that the variable x is operated concurrently by two threads, which can easily lead to misoperation. How can we solve this problem? With thread synchronization technology, plus synchronized keyword

public synchronized int fix (int y) {

return Testobj.fix (y);

}

Coupled with synchronization, you can see an orderly output from 9 to-10.

If the fix method added to the Testobj class can achieve synchronization?

public class testobj{

int x = 10;

public synchronized int fix (int y) {

return x = x-y;

}

}

If you add synchronized to a method, it is equivalent to

Synchronized (this) {

}