Synchronized Block v.s. Synchronized Method

[Jerry]

Anyone knows the differences between synchronized block and synchronized method?

Thanks!

 

[Andrew Thompson]

Anyone knows the differences between synchronized block and synchronized method?
Yep.

Thanks!

No worries.

BTW Jerry - do you mind trying to find these answers in the
books you were assigned for the course (or notes, handouts etc.)
rather than ask people on usenet to do your work/thinking for you?
<http://www.physci.org/codes/javafaq.jsp#homework>

As an aside, a better group for those learning Java is
<http://www.physci.org/codes/javafaq.jsp#cljh>

 

[Tor Iver Wilhelmsen]

Anyone knows the differences between synchronized block and synchronized method?

A synchronized method is a method with an implicit

synchronized (this) {

}

around all statements.

(or synchronized(MyClass.class) for static methods)

The difference is that an explicit synchronized block can span any
number of method statements, and can use any object for synchronizing
on.

 

[nicemothi]

Synchronized block Vs Synchronized method

First of all to achieve Multithreading mechanism in java we should go for synchronization. And this can be done in two ways depending on the requirement.

1. Synchronized block and
2. Synchronized method.

if you go for synchronized block it will lock a specific object.

if you go for synchronized method it will lock all the objects.

in other way Both the synchronized method and block are used to acquires the lock for an object. But the context may vary. Suppose if we want to invoke a critical method which is in a class whose access is not available then synchronized block is used. Otherwise synchronized method can be used.

Synchronized methods are used when we are sure all instance will work on the same set of data through the same function Synchronized block is used when we use code which we cannot modify ourselves like third party jars etc

For a detail clarification see the below code

for example:
//Synchronized block

class A
{ public void method1() {...} }
class B
{
public static void main(String s[])
{ A objecta=new A();
A objectb=new A();
synchronized(objecta){objecta.method1();}
objectb.method1(); //not synchronized
}
}


//synchronized method
class A
{ public synchronized void method1() { ...}
}
class B
{
public static void main(String s[])
{
A objecta=new A();
A objectb =new A();
objecta.method1(); objectb.method2();

}
}



Moti Lal D

 

[tonni]

Synchronized blocks

Synchronized methods are used when we are sure all instance will work on the same set of data through the same function Synchronized block is used when we use code which we cannot modify ourselves like third party jars etc

Synchronized blocks are quite useful also for many other situations. For example you can prevent a nested monitor problem where the code would otherwise go deadlock. In general they are a good way to separate code that needs synchronization from other stuff, which can sometimes speed up the program.