3、交换两个数字

        int a = 5;
        int b = 8;

//临时变量法
        int temp = b;
        b = a;
        a = temp;

//加减法
        a = a + b;
        b = a - b;
        a = a - b;

//异或法
        a = a ^ b;
        b = a ^ b;
        a = a ^ b;

        System.out.println("a = " + a);
        System.out.println("b = " + b);