StringBuffer类和String类的效率对比

处理字符串的StringBuffer类和String类时间效率对比。主要用到了System.currentTimeMillis();、append(); 。
我的java学习日记，不是技术文档哦。-- gt.liu - 20160321

测试代码如下：

//对比StringBuffer和String 的执行效率
import java.util.*;
public class Demo032003{
    public static void main(String [] args){
        //为了明显地看出两者的执行效率，分别将26个字母相加1000次
        String aaa = "abcdefghijklmnopqrstuvwxyz";
        int count = 1000;//叠加次数

        //String
        long timestart1 = System.currentTimeMillis();
        //System.out.println("timestart1 = " + timestart1 );//test currentTimeMillis();
        String str1 = "";
        for( int i = 0; i < count; i++ )
            str1 += aaa;
        long timeend1 = System.currentTimeMillis();
        System.out.println( "time1 = " + (timeend1 - timestart1) + "ms" );

        //StringBuffer
        long timestart2 = System.currentTimeMillis();
        StringBuffer str2 = new StringBuffer();
        for( int i = 0; i < count; i++ )
            str2.append(aaa);
        long timeend2 = System.currentTimeMillis();
        System.out.println( "time2 = " + (timeend2 - timestart2) + "ms" );

    }
}