Difference between String,StringBuffer, and StringBuilder

Difference between String and StringBuffer ?
====================================

=>String is Immutable (non changeable) and StringBuffer is Mutable (changeable)

=>String:-
=========

Once we create a String Object then we can’t perform any changes on that Object. If we are trying to perform any changes on that Object, then it will create a new Object

String s=new String("java");

s.concat("technology");
Output:- java
We can't perform concat operation on same object "s". 
------------------------------------------------------------------------------------

String s=new String("java");

String s1=s.concat("technology");
Output:- output is "javatechnology" and it store in new String Object "s1". But we can't perform concat operation on same object "s". 

=>StringBuffer:-
==============

Once we create a StringBuffer Object then we can perform any changes on that Object.

StringBuffer sb=new StringBuffer("java");

sb.append("technology");
Output:- javatechnology

public class Test {

   public static void main(String arg[])

   {

   String s=new String("java");

   s.concat("technology");

   System.out.println("String..."+s);

  

   StringBuffer sb=new StringBuffer("java");

   sb.append("technology");

   System.out.println("StringBuffer..."+sb);

   }

}

/*

Output:

String...java

StringBuffer...javatechnology

*/

Difference between StringBuffer and StringBuilder ?

StringBuffer:-
===========

=>It is synchronized i.e. thread safe. That mean two threads can’t perform operations on StringBuffer simultaneously.

StringBuilder:-
=============

=>StringBuilder is same like StringBuffer, but the difference is StringBuilder is non synchronized i.e, not thread safe. so two threads can perform operations on StringBuilder simultaneously.

public class Test {

   public static void main(String arg[])

   {

       StringBuffer sb=new StringBuffer("java");

       long time=System.currentTimeMillis();

       for(int i=0;i<=10000;i++)

       {

       sb.append("tech");

       }

       System.out.println("if synchronized time taken..."+(System.currentTimeMillis()-time)+"ms");

      

       StringBuilder s=new StringBuilder("java");

       time=System.currentTimeMillis();

        for(int i=0;i<=10000;i++)

       {

       s.append("tech");

       }

       System.out.println("if non-synchronized time taken..."+(System.currentTimeMillis()-time)+"ms");

      

   }

}

/*

Output:

if synchronized time taken...4ms

if non-synchronized time taken...1ms

*/