public class StringExample {
  public static void main(String[] args) {
  
    String string1 = new String("Hello");
    String string2, string3;
    int i;
  
    string2 = "world";
 
    string3 = string1 + string2;
    System.out.println(string3);
 
    string3 = string1 + " " + string2;
    System.out.println(string3);
 
    i = string3.indexOf("el");
    System.out.println(i);
 
    string3 = string3.replaceAll("l","ss");
    System.out.println(string3);
 
  }   
}