Can a lock be acquired on a class

Yes, a lock can be acquired on a class. This lock is acquired on the class's Class object..

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Sep 9th, 2005
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Aditya

Jul 26th, 2005

we can get lock on the class's Class object by using "static synchronize". This is the most exclusive lock.

Ajay Rout

Aug 27th, 2005

In class level the most exclusive lock can be achieved by synchronising the class's class object and declaring it static.

ramesh

Sep 9th, 2005

Classes can not be locked straightaway.
One can not tell

public synchronized class classname
{ }

But objects can be synchronized, also methods can be synchronized

abhishekgowl@yahoo.co.in
Profile Answers by abhishekgowl@yahoo.co.in Questions by abhishekgowl@yahoo.co.in

Oct 7th, 2005

Simply Locking a Thread means to do operation only at once you can Lock the Thread by simple put a keywork sychronize in the front of the method.
Like
Synchronize m1()
{
}

supari
Profile Answers by supari Questions by supari

Apr 21st, 2008

Aditya
Pls write code and explain

derrick.paul
Profile Answers by derrick.paul

Sep 12th, 2008

As your might already know, any synchronisation needs an object (monitor) to acquire lock one. See below for the three different types on how to synchronise code.
public class A
{
// A monitor object of sycnhronising piece of code.
   private Object mutex = new Object();

   // Type 1 - synchronise on current instance.
// This method locks on its own instance object. No other thread can access this method or any other synchronised instance method on this instance (ex. method4) till the current thread completes processing in method1.
public syncrhonized void method1()
{
}

// Type 2 - synchronise on the java.lang.Class Object of the this type.
// This method lock on the Class object created for this type. Every type has one class object created when the class file is loaded. No other thread can access this method or any other static method that is synchronsed in this class (ex. method5) till the current thread completes processing this method.
pubic static synchronized void method2()
{
}

// Type 3 - synchornise on any arbitary object.
// Though the method is not synchronised, the piece of code inside the sync block is thread safe. No other thread can access this piece of code until the current thread completes processing.
public void method3()
{
     // have some code here.
    synchronized (mutex)
    {
       // DO some thread safe stuff here.
     }
    // have some other code here.
}

public synchronized void method4(){}

public static synchronized void method5() {}
}

You cannot say something like: pubic synchronized class A

Type 1 and Type 2 are commonly used. But they block all peer methods. The efficient way is to use Type3 where you can specify which object to use as monitor.

Hope that helps.