Pass by value. How a wrapper works?

What will the following class print when run?

public class Sample{
   public static void main(String[] args)  {
     String s1 = new String("java");
     StringBuilder s2 = new StringBuilder("java");
     replaceString(s1);
     replaceStringBuilder(s2);
     System.out.println(s1 + s2);
  }
  static void replaceString(String s) {
     s = s.replace('j', 'l');
  }
  static void replaceStringBuilder(StringBuilder s) {
     s.append("c");
  }
}

answer: javajavac

String is immutable while StringBuilder is not. So no matter what you do in replaceString() method, the original String that was passed to it will not change. On the other hand,StringBuilder methods, such as replace or append, change the StringBuilder itself. So, 'c' is appended to java in replaceStringBuilder()  method.