import java.util.*; 
public class string {


     // String  str  = "hello";
     //

     public static void main(String[] args)
      {
        //  char[] strChar = {'h', 'e', 'l', 'l', 'o'};
        //    String str = "hello";
       
        //  System.out.println(str.hashCode());

        String s = "Hello World";

        
        String s2 = s.toLowerCase();
        String s3 = s.toUpperCase();
        Integer s4 = s.length();
     
        System.out.println(s2);
        System.out.println(s3);
        System.out.println(s4);

      
      }

        //Hello World 
        //lowercase it
        //uppercase it
        //reverse it
        //find the length
        //find the index of 'e'
        //find the index of 'l'
        //find substring from index 1 to 3
        //replace 'l' with 'm'
        //replace vs replaceAll
        //split it by ' '
        //trim it
        //concat it with " world" (with method)
        //contains
        //equals
        //equalsIgnoreCase
        //compareTo
        // == vs equals
        //difference between isBlank and isEmpty
        //starts with, ends with
}