两数交换

示例代码如下：
解法1

int n1 = 2;
int n2 = 4;
int temp;

temp = n1;
n1 = n2;
n2 = temp;

System.out.println(n1);
System.out.println(n2);

解法2

int n1 = 2;
int n2 = 4;
n1 = n1 + n2;
n2 = n1 - n2;
n1 = n1 - n2;
System.out.println(n1);
System.out.println(n2);

解法3

int n1 = 2;
int n2 = 4;
n1 = n1 ^ n2;
n2 = n1 ^ n2;
n1 = n1 ^ n2;
System.out.println(n1);
System.out.println(n2);

解法4

n1 = (n1 + n2) - (n2 = n1);
System.out.println(n1);
System.out.println(n2);