实例查看String与StringBuffer的性能差别

一个简单的例子,可以看出Java中的String和StringBuffer在拼接字串过程中所耗费的时间和空间的情况.

 

package net.moon.demo; import java.util.Date; public class Test { public static void main(String[] args) { Date d = new Date(); String s = ""; long r = Runtime.getRuntime().freeMemory(); StringBuffer sb = new StringBuffer(""); for (int i = 0; i < 10000; i++) { s += i; } System.out.println("String Memory used: " + ((r - Runtime.getRuntime().freeMemory()) / 1000) + "K"); System.out.println("String Time Used : " + (new Date().getTime() - d.getTime()) + " ms"); System.gc(); r = Runtime.getRuntime().freeMemory(); d = new Date(); for (int i = 0; i < 10000; i++) { sb.append(i); } System.out.println("StringBuffer Memory used: " + ((r - Runtime.getRuntime().freeMemory()) / 1000) + "K"); System.out.println("StringBuffer Time Used : " + (new Date().getTime() - d.getTime()) + " ms"); } }

运行后可以看出,String和StringBuffer之间性能的差别真的很大,不但运行时间上会有差别,在空间上的差别也是较大的.