How can I swap the string without third parameter?

In this program we we are using substring method to swap the String without third parameter. from substring we break string and compare from length.

					public class SwapString {
	public static void main(String[] args) {
		//declare two string
		String s1 = "hello";
		String s2 = "well";
		//string before swap
		System.out.println("before swap: "+s1+" - "+s2);
		//add second string from first
		s1=s1+s2; //hellowell
		s2=s1.substring(0, s1.length()-s2.length());
		System.out.println("after swap: "+s1+" - "+s2);

Output :-
before swap: hello – well
after swap: well – hello