java五种拼接字符串的方法

1. 原文件地址：http://www.cnblogs.com/focusj/archive/2011/02/16/2057630.html
2. package test;

import  org.apache.commons.lang.StringUtils;
public  class  CutString {
    //性能最差
    public  String testPlus() {
        String s = "" ;
        for  ( int  i = 0 ; i < 10000 ; i++) {
            s = s + String.valueOf(i);
        }
        return  s;
    }
    //较好
    public  String testConcat() {
        String s = "" ;
        for  ( int  i = 0 ; i < 10000 ; i++) {
            s = s.concat(String.valueOf(i));
        }
        return  s;
    }

    //性能与testStringBuffer相差无几，比其要好
    public  String testJoin() {
        String[] list = new  String[ 10000 ];
        for  ( int  i = 0 ; i < 10000 ; i++) {
            list[i] = String.valueOf(i);
        }
        return  StringUtils.join(list, "" );
    }
    public  String testStringBuffer() {
        StringBuffer sb = new  StringBuffer();
        long  l1 = System.currentTimeMillis();
        for  ( int  i = 0 ; i < 10000 ; i++) {
            sb.append(String.valueOf(i));
        }
        long  l2 = System.currentTimeMillis();
        System.out.println(l2-l1);
        return  sb.toString();
    }

    //性能最高的方法
    public  void  testStringBuilder() {
        StringBuilder sb = new  StringBuilder();
        for  ( int  i = 0 ; i < 100000 ; i++) {
            sb.append(String.valueOf(i));
        }
        sb.toString();
    }
    public  static  void  main(String[] args) {
        System.out.println( new  CutString().testStringBuffer());
    }
}