this keyword1--java

import java.io.*;
class Demo42
{
public static void main(String args[])
{
int a=10,b=20;
Numbers n=new Numbers(a,b);
Swapping s=new Swapping();
System.out.println("before swapping"+n.a+n.b);
s.swap(n);
System.out.println("after swapping"+n.a+n.b);
}
}
class Numbers
{
int a,b;
public Numbers(int a, int b)
{
this.a=a;
this.b=b;
}
}
class Swapping
{
public void swap(Numbers n)
{
int temp;
temp=n.a;
n.a=n.b;
n.b=temp;
}
}