Replacing a String in a pgm

Replacing a String

public class StringReplaceEmp

{

   public static void main(String args[])

  {

      String str="Hello World";

      System.out.println( str.replace( 'H','W' ) );

      System.out.println( str.replaceFirst("He", "Wa") );

      System.out.println( str.replaceAll("He", "Ha") );

   }

}