Difference between StringBuilder and StringBuffer

Question

What is the main difference between StringBuffer and StringBuilder? Is there any performance issues when deciding on any one of these?

Answer 1

StringBuffer is synchronized, StringBuilder is not.

Answer 2

StringBuilder is faster than StringBuffer because it's not synchronized.

Here's a simple benchmark test:

public class Main {     public static void main(String[] args) {         int N = 77777777;         long t;          {             StringBuffer sb = new StringBuffer();             t = System.currentTimeMillis();             for (int i = N; i --> 0 ;) {                 sb.append("");             }             System.out.println(System.currentTimeMillis() - t);         }          {             StringBuilder sb = new StringBuilder();             t = System.currentTimeMillis();             for (int i = N; i > 0 ; i--) {                 sb.append("");             }             System.out.println(System.currentTimeMillis() - t);         }     } } 

A test run gives the numbers of 2241 ms for StringBuffer vs 753 ms for StringBuilder.