Java程序填空，已知变量a、b的值，要求交换a、b的值并输出到屏幕上

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

// routine to exchange a, b
...

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

==================================
// routine to exchange a, b
...

直接：
int tmp = a;
a = b;
b = a;

不用中间量：
a = a + b;
b = a - b;
a = a - b;

不用中间量且不担心溢出：使用 bitwise Xor
a = a ^ b;
b = a ^ b;
a = a ^ b;

a=a+b;
b=a-b;
a=a-b;

int temp = a;

a = b;
b = temp;

楼上两种方法都可以，一种是借助中间变量temp，另一种不用中间变量，也有的面试题要求必须不使用中间变量的

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