几种拼接字符串的效率问题 .

public class test {

/**

* @param args

*/

public static void main(String[] args) {

// TODO Auto-generated method stub

long n = 30000;

System.out.println("Start... "+n);

long start1 = System.currentTimeMillis();

String s1 = new String("hello");

for (long i = 0; i < n; i++)

{

s1+="拼接字符串的时间";

}

long end1 = System.currentTimeMillis();

long time1 = end1 -start1;

System.out.println("用String+=拼接字符串的时间"+time1);

long start2 = System.currentTimeMillis();

String s2 = new String("hello");

for (long i = 0; i < n; i++)

{

s2=s2+"拼接字符串的时间";

}

long end2 = System.currentTimeMillis();

long time2 = end2 -start2;

System.out.println("用String=String+拼接字符串的时间"+time2);

long start3 = System.currentTimeMillis();

String s3 = new String("hello");

for (long i = 0; i < n; i++)

{

s3=s3.concat("拼接字符串的时间");

}

long end3 = System.currentTimeMillis();

long time3 = end3 -start3;

System.out.println("用String.concat拼接字符串的时间"+time3);

long start4 = System.currentTimeMillis();

StringBuffer s4 = new StringBuffer("hello");

for (long i = 0; i < n; i++)

{

s4.append("拼接字符串的时间");

}

long end4 = System.currentTimeMillis();

long time4 = end4 -start4;

System.out.println("用StringBuffer.append拼接字符串的时间"+time4);

long start5 = System.currentTimeMillis();

StringBuilder s5 = new StringBuilder("hello");

for (long i = 0; i < n; i++)

{

s5.append("拼接字符串的时间");

}

long end5 = System.currentTimeMillis();

long time5 = end5 -start5;

System.out.println("用StringBuilder.append拼接字符串的时间"+time5);

System.out.println("End...");

}

}

贴出一组检测数据如下:

[java] view plaincopy





用String+=拼接字符串的时间27468

用String=String+拼接字符串的时间25813

用String.concat拼接字符串的时间12265

用StringBuffer.append拼接字符串的时间14

用StringBuilder.append拼接字符串的时间8