Integer a =1 , b= 2;
        System.out.println("before:a="+a+"  b="+b);
        Field field = Integer.class.getDeclaredField("value");
        field.setAccessible(true);
        int temp = a.intValue();
        System.out.println("before:temp="+temp);
        field.set(a,b.intValue());
        System.out.println("after:temp="+temp);
      
        field.set(b,temp);
        System.out.println("after:a="+a+"  b="+b);

        Integer c= Integer.valueOf(1);
        Integer d= Integer.valueOf(2);
        Integer e= new Integer(1);
        System.out.println("before:c="+c+"  d="+d +"  e="+e);
 

題目很簡單，你做對了嗎？

        Integer a =1 , b= 2;
        System.out.println("before:a="+a+"  b="+b);
        Field field = Integer.class.getDeclaredField("value");
        field.setAccessible(true);
        int temp = a.intValue();
        System.out.println("before:temp="+temp);
        field.set(a,b.intValue());
        System.out.println("after:temp="+temp);
        //set()的引數是Object，Object,而Object是引用型別，不是基本型別！所以這裡傳入的int 
          temp=1,還需要先自動包裝成Integer，即Integer.valueOf(temp)
        //最後，利用反射給int value這個欄位設值的時候，其實使用到的是Integer.intValue()值
        field.set(b,Integer.valueOf(temp).intValue());
        field.set(b,temp);
        System.out.println("after:a="+a+"  b="+b);

        Integer c= Integer.valueOf(1);
        Integer d= Integer.valueOf(2);
        Integer e= new Integer(1);
        System.out.println("before:c="+c+"  d="+d +"  e="+e);
 

before:a=1  b=2
before:temp=1
after:temp=1
after:a=2  b=2
before:c=2  d=2  e=1

Process finished with exit code 0