public class Test{
         public static void main(String[] args){
                     int a=1;
                     int b=2;
                     int c=a;
                     a=b;//a=2
                     b=c;//b=1
         }
}

public class Test{
         public static void main(String[] args){
                     int a=1;
                     int b=2;
                     a=a+b;
                     b=a-b;//b=1
                     a=a-b;//a=2
         }
}  

public class Test{
         public static void main(String[] args){
                     int a=1;
                     int b=2;
                     a=a^b;//a先用来储存a和b异或运算的中间值
                     b=a^b;//b=1
                     a=a^b;//a=2
         }
}