pubpc class MyClass{
  private Object num;

  pubpc MyClass(Object num){
    this.num=num;
  }
  
  pubpc Object getNum() {
    return num;
  }

  pubpc void setNum(Object num) {
    this.num = num;
  }
}

pubpc class Main {
  
  pubpc static void change(MyClass myClass){
    myClass.setNum(100);
  }
  
  
  
  pubpc static void main(String[] args){
    MyClass a=new MyClass(10);
    System.out.println("调用change方法前的值为："+a.getNum());
    change(a);
    System.out.println("调用change方法后的值为："+a.getNum());
  }
  
}

pubpc static void swap(MyClass a,MyClass b){
    MyClass tmp=a;
    a=b;
    b=tmp;
  }
  
  pubpc static void main(String[] args){
    MyClass a=new MyClass(10);
    MyClass b=new MyClass(100);
    System.out.println("交换之前a的值为："+a.getNum());
    System.out.println("交换之前b的值为："+b.getNum());
    swap(a,b);
    System.out.println("交换之后a的值为："+a.getNum());
    System.out.println("交换之后b的值为："+b.getNum());
  }
}

pubpc static void swap(MyClass a,MyClass b){
    Object tmp=a.getNum();
    a.setNum(b.getNum());
    b.setNum(tmp);
}