A simple but profound interview questions: how the exchange value of the two numbers by the method

/ ** 
 * transmitted by the process of how the reference values of the two exchange numbers 
 * 
 * @author zhuliang 
 * @date 2019/7/14 10:39 
 * / 
public  class SwapValueDemo { 

    public  static  void main (String [] args) throws Exception { 
        A Integer =. 1 ; 
        Integer B = 2 ; 
        System.out.println ( "before exchanging = A" + + A ", B =" + ; B) 
        the swap (A, B); 
        System.out.println ( "after exchange = A "+ + A", B = "+ B); 
    } 

    / ** 
     * number of errors in two exemplary switching 
     * 
     * @paramA 
     * @param B
      * / 
    Private  static  void falseSwap (A Integer, Integer B) {
         int TEMP = A; 
        A = B; 
        B = TEMP; 
    } 

    / ** 
     * by reflecting the switching values of the two numbers 
     * result 
     * exchange before 1 = A, b = 2 
     * 2 = after the exchange A, b = 2 
     * Why is this so? 
     * <P> 
     * caching mechanism because there is integer 
     * { @link Integer.IntegerCache.low = -128} 
     * { @link Integer.IntegerCache.high} = 127 
     * Because a = 1, b = 2 
     * in int temp = a.intValue (); This line , the acquired value of 1 is present in the cache 
     * in value.set (a, b); after this line, the value of a to 2 
     * a.intValue is because the basic data types, the address itself can represent value, resulting in just temp value also becomes a 2 
     * then call value.set (b, temp); time will be assigned to the 2 b 
     the final result is a so * 2 = a, B = 2 
     * <P> 
     * solve this problem there are two ways 
     * 1 the values a, b is a number greater than transducer 127 or less than -128, so as to not We use the caching mechanism Integer 
     * 2 used when the assignment to the new Integer temp manner, to obtain a new address 
     * 
     * @param a 
     * @param B
      * / 
    Private  static  void the swap (a Integer, Integer B) throws Exception { 
        value Field, = Integer. class .getDeclaredField ( "value" );
        value.setAccessible(true);
//        int temp = a.intValue();
        Integer temp = new Integer(a.intValue());
        value.set(a, b);
        value.set(b, temp);
    }

}