Many of you might know, the String concat(+) is costly operation compare to StringBuffer or StringBuilder append() method. But you might not know the actual performance difference. Let me show you the performance difference with a simple test program, package test; public class StrVsBuffVsBuild { public static void main(String[] args) { int count=200000; System.out.println(“Number of Strings concat Operation is ‘”+count+”‘”); long st = System.currentTimeMillis(); String str = “”; for (int i = 0; i < count; i++) { str += "MyString"; } System.out.println("Time taken for String concat (+) Operation is '"+(System.currentTimeMillis()-st)+"' Millis"); st = System.currentTimeMillis(); StringBuffer sb = new StringBuffer(); for (int i = 0; i < count; i++) { sb.append("MyString"); } System.out.println("Time taken for StringBuffer.append() Operation is '"+(System.currentTimeMillis()-st)+"' Millis"); st = System.currentTimeMillis(); StringBuilder sbr = new StringBuilder(); for (int i = 0; i < count; i++) { sbr.append("MyString"); } System.out.println("Time taken for StringBuilder.append() Operation is '"+(System.currentTimeMillis()-st)+"' Millis"); } } Following are the output of the above test program, Number of Strings concat Operation is '200000' Time taken for String concat (+) Operation is '373933' Millis Time taken for StringBuffer.append() Operation is '19' Millis Time taken for StringBuilder.append() Operation is '5' Millis The String concat (+) took 6.2 Minutes , however others took only 19 / 5 milliseconds
