Java - Check String 2

public class cks
{
   public static void main(String args[])
   {
       String s1, s2, s3, s4, output;

       s1 = new String("x");
       s2 = new String("y");
       s3 = new String("abc xyz");
       s4 = new String("Abc Xyz");

       output = "s1 = " + s1 + "\n" +
                "s2 = " + s2 + "\n" +
                "s3 = " + s3 + "\n" +
                "s4 = " + s4 + "\n\n";
       //--------------------------------------------
       // test with 'equals'
       //--------------------------------------------
       if (s1.equals("x"))
                    output +=     "s1.equals \"x\"\n";
       else         output += "not s1.equals \"x\"\n";
       //--------------------------------------------
       // test with '=='
       //--------------------------------------------
       if (s1 == "x")
                    output +=     "s1 == \"x\"\n";
       else         output += "not s1 == \"x\"\n";
       //--------------------------------------------
       // test for equality (ignore case)
       //--------------------------------------------
       if (s3.equalsIgnoreCase(s4))
                    output +=     "s3.equalsIgnoreCase(s4)\n";
       else         output += "not s3.equalsIgnoreCase(s4)\n";
       //--------------------------------------------
       // test compareTo
       //--------------------------------------------
       output += "\ns1.compareTo(s2) is " + s1.compareTo(s2) +
                 "\ns2.compareTo(s1) is " + s2.compareTo(s1) +
                 "\ns1.compareTo(s1) is " + s1.compareTo(s1) +
                 "\ns3.compareTo(s4) is " + s3.compareTo(s4) +
                 "\ns4.compareTo(s3) is " + s4.compareTo(s3) +"\n\n";
       //--------------------------------------------
       // test regionMatches (case sensitive)
       //--------------------------------------------
       if (s3.regionMatches(0, s4, 0, 3))
               output += "1st 3 letters of s3 & s4 match\n";
       else    output += "1st 3 letters of s3 & s4 do not match\n";
       //--------------------------------------------
       // test regionMatches (true = ignore case)
       //--------------------------------------------
       if (s3.regionMatches(true, 0, s4, 0, 3))
             output += "1st 3 letters of s3 & s4 match";
       else  output += "1st 3 letters of s3 & s4 do not match";

      System.out.println(output);
   }
}