促成java多线程死锁的代码

造成java多线程死锁的代码
private　Object ob1 = new Object();
private Object ob2 = new Object();

public void call1(){
   synchronized(ob1){
     synchronized(obj2){
      doing.....
     }
  }
}
public void call2(){
   synchronized(obj2){
      synchronized(obj1){
      doing...
  }
}
}