Difference between String buffer and String builder in Java

String buffer and StringBuilder both are mutable classes which can be used to do operation on string objects such as reverse of string, concating string and etc. We can modify string without creating a new object of the string.

A string buffer is thread-safe whereas string builder is not thread-safe. Therefore, it is faster than a string buffer. Also, a string concat + operator internally uses StringBuffer or StringBuilder class. Below are the differences.

Sr. No. Key String Buffer String Builder
1 Basic StringBuffer was introduced with the initial release of Java It was introduced in Java 5
2 Synchronized It is synchronized It is not synchronized
3 Performance It is thread-safe. So, multiple threads can’t access at the same time, therefore, it is slow. It is not thread-safe hence faster than String Buffer.
4 Mutable It is mutable. We can modify string without creating an object. It is also mutable
5 Storage Heap Heap

Example of StringBuilder

public class StringBuilderExample{
   public static void main(String[] args){
      StringBuilder builder=new StringBuilder("Hi");
      builder.append("Java 8");
      System.out.println("StringBuilderExample" +builder);


StringBuilderExampleHiJava 8 

Example of StringBuffer

public class StringBufferExample{
   public static void main(String[] args){
      StringBuffer buffer=new StringBuffer("Hi");
      buffer.append("Java 8");
      System.out.println("StringBufferExample" +buffer);


StringBufferExampleHiJava 8 

Updated on: 05-Dec-2023

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