C++字符串拼接效率对比(+=、append、stringstream、sprintf)

#include <iostream>
#include <string>
#include <sys/time.h>
#include <sstream>
#include <stdio.h>
using namespace std;
#define OUT_IN_REPEATE_NUM 100000
#define IN_REPEATE_NUM 100  //内层循环将s1、s2、s3循环拼接100次
string s1="aaaaaa";
string s2="bbbbbb";
string s3="cccccc";
void  plusTest(string& ret)
{
    for(int i=0; i<IN_REPEATE_NUM; i++)
    {
        ret += s1;
        ret += s2;
        ret += s3;
    }
}
void  appendTest(string& ret)
{
    for(int i=0; i<IN_REPEATE_NUM; i++)
    {
        ret.append(s1);
        ret.append(s2);
        ret.append(s3);
    }
}
void sprintfTest(string& ret)
{
    const size_t length=26*IN_REPEATE_NUM;
    char tmp[length];
    char* cp = tmp;
    size_t strLength=s1.length()+s2.length()+s3.length();
    for(int i=0; i<IN_REPEATE_NUM; i++)
    {
        sprintf(cp,"%s%s%s", s1.c_str(), s2.c_str(),s3.c_str());
        cp+=strLength;
    }
    ret = tmp;
}
void  ssTest(string& ret)
{
    stringstream ss;
    for(int i=0; i<IN_REPEATE_NUM; i++)
    {
        ss<<s1;
        ss<<s2;
        ss<<s3;
    }
    ret = ss.str();
}
int main() {
    string ss, plus, append, sprintf;
    struct timeval sTime, eTime;
    gettimeofday(&sTime, NULL);
    for(int i=0; i<OUT_IN_REPEATE_NUM; i++)
    {
        sprintf="";
        sprintfTest(sprintf);
    }
    gettimeofday(&eTime, NULL);
    long SprintfTime = (eTime.tv_sec-sTime.tv_sec)*1000000+(eTime.tv_usec-sTime.tv_usec); //exeTime 单位是微秒
    gettimeofday(&sTime, NULL);
    for(int i=0; i<OUT_IN_REPEATE_NUM; i++)
    {
        append="";
        appendTest(append);
    }
    gettimeofday(&eTime, NULL);
    long AppendTime = (eTime.tv_sec-sTime.tv_sec)*1000000+(eTime.tv_usec-sTime.tv_usec); //exeTime 单位是微秒
    gettimeofday(&sTime, NULL);
    for(int i=0; i<OUT_IN_REPEATE_NUM; i++)
    {
        ss="";
        ssTest(ss);
    }
    gettimeofday(&eTime, NULL);
    long SsTime = (eTime.tv_sec-sTime.tv_sec)*1000000+(eTime.tv_usec-sTime.tv_usec); //exeTime 单位是微秒
    gettimeofday(&sTime, NULL);
    for(int i=0; i<OUT_IN_REPEATE_NUM; i++)
    {
        plus="";
        plusTest(plus);
    }
    gettimeofday(&eTime, NULL);
    long PlusTime = (eTime.tv_sec-sTime.tv_sec)*1000000+(eTime.tv_usec-sTime.tv_usec); //exeTime 单位是微秒
    cout<<"PlusTime is :   "<<PlusTime<<endl;
    cout<<"AppendTime is : "<<AppendTime<<endl;
    cout<<"SsTime is :     "<<SsTime<<endl;
    cout<<"SprintfTime is :"<<SprintfTime<<endl;
    if(ss==sprintf && append==plus && ss==plus)
    {
        cout<<"result string are same!"<<endl;
    }
    else
    {
        cout<<"Different!"<<endl;
        cout<<"Sprintf: "<<sprintf<<endl;
        cout<<"ss:        "<<ss<<endl;
        cout<<"Plus:     "<<plus<<endl;
        cout<<"Append:"<<append<<endl;
    }
}

void* test_stringstream(void * arg)
{
	stringstream oss;
	for(int i=0;i<10000;i++)
	{
		oss.clear();这仅仅置流标记
		oss.str("");/这是才是真正清空操作
		oss << i;
	}
}

public static void main(String[] args) {
        long start = 0L;
        long end = 0L;
        System.out.println("字符串拼接执行效率比较：");
        String s1 = "";
        start = System.currentTimeMillis();
        for (int i = 0; i < 100000; i++) {//十万次
        	s1 = s1 + "a";
        }
        end = System.currentTimeMillis();
        System.out.println("1、+ 方式拼接10万次耗时：" + (end - start) + "毫秒!");
        String s2 = "";
        start = System.currentTimeMillis();
        for (int i = 0; i < 100000; i++) {//十万次
        	s2 += "b";
        }
        end = System.currentTimeMillis();
        System.out.println("2、+= 方式拼接10万次耗时：" + (end - start) + "毫秒!");
        StringBuffer bf = new StringBuffer();
        start = System.currentTimeMillis();
        for (int i = 0; i < 10000000; i++) {//千万次
        	bf.append("c");
        }
        end = System.currentTimeMillis();
        System.out.println("3、StringBuffer.append 方式拼接1000万次耗时：" + (end - start) + "毫秒!");
        StringBuilder bl=new StringBuilder();
        start = System.currentTimeMillis();
        for (int i = 0; i < 10000000; i++) {//千万次
        	bl.append("d");
        }
        end = System.currentTimeMillis();
        System.out.println("4、StringBuilder.append 方式拼接1000万次耗时：" + (end - start) + "毫秒!");
	}