java在一个void函数中，交换两个数的值

import java.lang.reflect.Field;

public class Main {

    public static void main(String[] args) {

        Integer a = 1;
        Integer b = 2;
        System.out.println("before swap a=" + a + ";b=" + b);
        swap(a, b);
        System.out.println("after swap a=" + a + ";b=" + b);
    }

    private static void swap(Integer num1, Integer num2) {
//        System.out.println("after swap a=" + num2 + ";b=" + num1);
//        System.exit(0);
        try {
            Field field = Integer.class.getDeclaredField("value");
            field.setAccessible(true);
            int tmp = num1;
            field.set(num1, num2);
            //IntegarCache的缓存范围[-128,127]
            field.set(num2, new Integer(tmp));

        } catch (NoSuchFieldException | IllegalAccessException e) {
            e.printStackTrace();
        }

    }


}