Static synchronization in java

Static synchronization is achieved by static synchronized methods. Static synchronized method locked on class and non-static synchronized method locked on current object i.e. static and non-static synchronized methods can run at same time. It can produce inconsistency problem.

If static synchronized method is called a class level lock is acquired and then if an object is tries to access non-static synchronized method at the same time it will not be accessible because class level lock is already acquired.

Example:

MultiThreadExample.java

/**
 * This program is used to show the multithreading 
 * example with synchronization using static synchronized method.
 * @author w3spoint
 */
class PrintTable{    
    public synchronized static void printTable(int n){
	   System.out.println("Table of " + n);
       for(int i=1;i<=10;i++){
           System.out.println(n*i);  
           try{  
        	 Thread.sleep(500);  
           }catch(Exception e){
        	 System.out.println(e);
           }  
        }         
    }  
}  
 
class MyThread1 extends Thread{    
    public void run(){ 
    	PrintTable.printTable(2);  
    }        
}  
 
class MyThread2 extends Thread{   
	public void run(){  
		PrintTable.printTable(5);  
	}  
}  
 
public class MultiThreadExample{  
    public static void main(String args[]){
 
    	//creating threads.
	    MyThread1 t1=new MyThread1();  
	    MyThread2 t2=new MyThread2();  
 
	    //start threads.
	    t1.start();  
	    t2.start();  
    }  
}

Output:

Download this example.

Difference between static and non-static synchronized method.

Non-Static synchronized method	Static synchronized method
Lock is on object. Commonly used. Static keyword is not used.	Lock is on class. Not commonly used. Used with static keyword.

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