关于不用第三变量交换2个变量的值???

法一：
public class Test {
public static void main(String[] args) {
int a = 1;
int b = 2;
a = b + (b = a) * 0;  //这句实现交换
System.out.println("a:" + a + "  b:" + b);
}
}

法二：
public class Person {  
 
    public static void main(String[] args) {  
        //利用一个数异或本身等于０和异或运算符合交换率  
        int a = 10, b = 5;  
        a = a ^ b;  
        b = a ^ b;  
        a = a ^ b;  
          
        System.out.println("a=" + a + "\nb=" + b);  
    }  
} 

法三：
public class Person {  
 
    public static void main(String[] args) {  
        //利用加减法  
        int a = 10, b = 5;  
        a = a + b;  
        b = a - b;  
        a = a - b;  
          
        System.out.println("a=" + a + "\nb=" + b);  
    }  
}