I have started learning synchronization in threading.
Synchronized method:
public class Counter {
private static int count = 0;
public static synchronized int getCount() {
return count;
}
public synchronized setCount(int count) {
this.count = count;
}
}
Synchronized block:
public class Singleton {
private static volatile Singleton _instance;
public static Singleton getInstance() {
if (_instance == null) {
synchronized(Singleton.class) {
if (_instance == null)
_instance = new Singleton();
}
}
return _instance;
}
}
When should I use synchronized
method and synchronized
block?
Why is synchronized
block better than synchronized
method ?
It's not a matter of better, just different.
When you synchronize a method, you are effectively synchronizing to the object itself. In the case of a static method, you're synchronizing to the class of the object. So the following two pieces of code execute the same way:
public synchronized int getCount() {
// ...
}
This is just like you wrote this.
public int getCount() {
synchronized (this) {
// ...
}
}
If you want to control synchronization to a specific object, or you only want part of a method to be synchronized to the object, then specify a synchronized
block. If you use the synchronized
keyword on the method declaration, it will synchronize the whole method to the object or class.