StringBuffer

StringBuffer class is similar to String class except that strings created using StringBuffer objects are mutable( modifiable).

1. StringBuffer objects are mutable
2. Multiple StringBuffer operations modify the same object
3. StringBuffer objects are thread-safe like String objects

How to create a StringBuffer object

1. In the first way, it can be created using the new keyword

StringBuffer obj = new StringBuffer("Meera");

Create StringBuffer object from String object

String s = "Meera";

StringBuffer obj = new StringBuffer(s);

Create String object from StringBuffer object

StringBuffer obj = new StringBuffer("Meera");
String s = obj.toString();

StringBuffer Example for append method

package com.javatrainingschool;

public class StringBufferExample {

	public static void main(String[] args) {
		
		StringBuffer sb = new StringBuffer("Anjali");
		
		sb.append(" Kumar");
		
		System.out.println(sb);	
	}
}

Output:
Anjali Kumar

StringBuffer example2

package com.javatrainingschool;

public class StringBufferExample {

	public static void main(String[] args) {
		
		StringBuffer sb = new StringBuffer("Anjali");
		
		sb.append(" Kumar");
		
		System.out.println(sb);	
		
		//Displays the current capacity of the string buffer object
		System.out.println(sb.capacity());
		
		//deletes the character from index 2 to 5(excluding)
		sb.delete(2, 5);
		
		System.out.println(sb);
	}
}

Output:

Reverse a String using StringBuffer’s reverse method

package com.javatrainingschool;

public class StringBufferExample {

	public static void main(String[] args) {
		
		String s = "Kishor Kumar";
		System.out.println("Original String : " + s);
		
		StringBuffer sb = new StringBuffer(s);
		
		sb.reverse();
		
		s = sb.toString();
		System.out.println("Reversed String : " + s);
	}
}

Output:

Conlusion:

From the above examples, it is clear that which operations we do on StringBuffer objects affect the original string. It is not true in case of String objects. Each operation on String object creates a new String object altogether.

When to use StringBuffer instead of String

When there are repeated operations like concatenation, replace, delete, insert etc on the string objects, it is better to go with StringBuffer class rather than the String class.