Automation Using Selenium Webdriver

Monday 26 December 2016

String vs stringbuffer vs stringbuilder

1.Definition:

  • String is an immutable sequence of characters.
  • StringBuffer is mutable sequence of characters.
  • StringBuilder is also mutable sequence of characters.

The only difference between StringBuffer and StringBuilder: 

  • StringBuffer object is thread safe , it means StringBuffer object is modified by multiple concurrently, because  all its methods are declared as "synchronized".
  • StringBuilder class is given in jdk 1.5 version as non thread -safe class, means all its methods are non synchronized methods.
  • So , in single model application we must use StringBuilder, so that object locking and unlocking will not be there, hence performance is increased.
  • In single thread model application operations are executed in sequence hence there is no chance of object corruption.

When should we choose String and StringBuffer? 

  • If we do not want to store string modifications in the same memory we must choose String.
  • To do modifications in the same memory, we must choose StringBuffer or StringBuilder.

 Advantage and disadvantage in String: 

  • Advantage : Since modifications are preserving in another memory location, we will have both original and modified values.
  • Disadvantage: It consumes lot memory for every operation, as it stores it modifications in new memory. So it leads to performance issue.
  • Solution: To solve this performance issue , in projects developers store string data using StringBuilder or StringBuffer after all modifications they convert into String and pass it back to user.

Advantage and disadvantage of StringBuffer or StringBuilder:

  • Advantage: It given high performance because consumes less memory as all modifications stored in same memory.
  • Disadvantage: Original value will not be preserved.

2.Creating String , StringBuffer objects: 

String:

  • String object can be created in two ways.
  • By using string literal : String str="instance of java ";
  • By using its constructors: String str= new String("instaneofjavaforus") ;

StringBuffer:

  • By using its available constructors
  • StringBuffer str= new StringBuffer();

StringBuilder:

  • By using its available constructors
  • StringBuilder str= new StringBuilder ();

3.Special operations those we can only perform on StringBuffer and StringBuilder: 

  1. append
  2. insert
  3. delete
  4. reverse
  •  Since string is immutable we cannot perform these operations on String.

4.Concatenation:

  • Using String object we can concat new string to the current  string in two ways.
  1. Using + operator
  2. using concat() method.
  • Using StringBuffer we can perform concat operation only in one way
  1. Using append() method
  • Using StringBuilder we can perform concat operation only in one way
  1. Using append() method
package com.javaforus;
public Class SBDemo{ 
public static void main (String args[]) {
        String str="Java";
        StringBuffer sb= new StringBuffer("Java");
        StringBuilder sbr= new StringBuilder("Java");
       System.out.println(str.concat(" language"));    
       System.out.println(sb.append(" language"));
        System.out.println(sbr.append(" language"));
}
}
OutPut:
Java language
Java language
Java language

5.Comparison:

  • Using equals() method String objects are compared with state, because it is overridden in this class. Also hashcode(0 method is overridden in order to satisfy equals() method contract.
  • But in StringBuffer and in StringBuilder equals() method is not overridden , so using equals() method their object are compared with reference. 

1 comment: