Locking at object level can be achieved by marking a non-static block of code or non-static method (the lock object for that method's object) with synchronized. In the following examples, only one thread at a time will be allowed to execute the synchronized method/block on the given instance of the class:

• Synchronized method case:

public class ClassOll {
  public synchronized void methodOll() {
    ...
  }
}

• Synchronized block of code:

public class ClassOll {
  public void methodOll() {
    synchronized(this) {
      ...
    }
  }
}

• Another synchronized block of code:

public class ClassOll {

  private final Object ollLock = new Object();
  public void methodOll() {
    synchronized(ollLock) {
      ...
    }
  }
}