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.