java program to swap two numbers

How to swap two numbers without using temporary variable:

public class SwappingNumbers{
     public static void main(String []args){
        int a=10,b=20;
        a=a*b;
        b=a/b;
        a=a/b;
                System.out.println("a = "+a);
                System.out.println("b = "+b);
     }
}

Output:
                        a = 20
                        b = 10


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