Common Synchronization Bug

1. What's wrong with this code?

public class SomeThreadedClass extends Thread {
  private static Vector sharedObject; //shared data
  private Integer localObject;        //not shared

  private void accessSomeSharedObject() {
    // change values in sharedObject
    ...
  } 

  public synchronized void doSomeOperation() { 
    accessSomeSharedObject();
  }

  public void run() {
    while(someCondition) {
      doSomeOperation();      // accesses shared data
      doSomeOtherOperation(); // no shared data
    }
  }

  public void doSomeOtherOperation() {
    // change values in localObject
    ...
  }
  ...
}

2. Problem

The doSomeOperation synchronizes on this. Each instance of SomeThreadedClass observes a separate this; thus, the synchronized method does not block the other threads from accessing sharedObject and a race condition can occur (in fact, each SomeThreadedClass instance executes in a separate run method).