Nilhar technology

String : String Objects are immutable. when we create a String object and we performed some operation on String the new reference is created. For Example :  String s1 = new String("Hello"); s1.concate("Java");/now original string is not changed. new reference is created in memory.  System.out.println("String Value"+ s1); In the above example output is "Hello" because s1 is immutable. StringBuffer : StringBuffer is mutable. when we create a StringBuffer object and we performed some operation on StringBuffer then it changes in the same object/Reference. StringBuffer sb=new StringBuffer("Hello ");   sb.append("Java");//now original string is changed   System.out.println(sb);//prints Hello Java   In the Above Example output is hello Java because sb is mutable.