主题：【倡议】Java SE 5.0和.NET 2.0擂台赛 -- Highway

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老大河待整

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复 String, StringBuffer &StringBuilder的玄妙

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我对Java StringBuffer/StringBuilder的测试结果

首先，我对老轧的程序进行了一些简单的修改，主要如下：

一。取消了对String的测试部分，而只测试StringBuffer和StringBuilder，因为String的性能明显落后，测试的意义不大。

二。测试范围从1000到100，000，步长为1000，这样可以看出一些比较细的东西。

三。每组测试后，我调用了System.gc()来建议JVM立刻进行内存回收，其目的是最小化前次试验对后续试验由于不定期的内存回收所造成的性能震荡。

其次，我的实验分为使用-Client和-Server两种，目的是比较不同参数下的同级别测试的性能差异，另外，所使用的参数还包括了-Xms256M -Xmx256M。

下面是我的测试代码：

package test2005_2;

class StringTest {

private String[] prepareString(int number) {

System.out.println("String number: " + number);

String[] strs = new String[number];

for (int i = 0; i < number; i++) {

strs[i] = "Highway" + i;

}

return strs;

}

private void stringBuilderTest(String[] input) {

long start = System.currentTimeMillis();

StringBuilder sb = new StringBuilder();

for (int i = 0; i < input.length; i++) {

sb.append(input[i]);

}

long time = System.currentTimeMillis() - start;

System.out.println("StringBuilder Takes Time: " + time + "ms");

}

private void stringBufferTest(String[] input) {

long start = System.currentTimeMillis();

StringBuffer sb = new StringBuffer();

for (int i = 0; i < input.length; i++) {

sb.append(input[i]);

}

long time = System.currentTimeMillis() - start;

System.out.println("StringBuffer Takes Time: " + time + "ms");

}

public void test() {

String[] strs = null;

for (int i = 1; i <= 100; i++) {

strs = this.prepareString(i * 1000);

this.stringBufferTest(strs);

this.stringBuilderTest(strs);

System.gc();

}

public static void main(String[] args) {

StringTest stringtest = new StringTest();

stringtest.test();

}

下面是使用了-Server -Xms256M -Xmx256M参数情况下的测试结果：

String number: 1000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 2000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 3000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 0ms

String number: 4000

StringBuffer Takes Time: 31ms

StringBuilder Takes Time: 0ms

String number: 5000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 6000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 7000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 8000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 9000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 10000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 11000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 12000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 13000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 14000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 15000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 0ms

String number: 16000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 17000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 0ms

String number: 18000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 16ms

String number: 19000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 0ms

String number: 20000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 16ms

String number: 21000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 16ms

String number: 22000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 15ms

String number: 23000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 0ms

String number: 24000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 16ms

String number: 25000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 0ms

String number: 26000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 15ms

String number: 27000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 16ms

String number: 28000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 16ms

String number: 29000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 31ms

String number: 30000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 16ms

String number: 31000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 0ms

String number: 32000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 31ms

String number: 33000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 16ms

String number: 34000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 16ms

String number: 35000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 15ms

String number: 36000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 16ms

String number: 37000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 15ms

String number: 38000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 16ms

String number: 39000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 16ms

String number: 40000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 16ms

String number: 41000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 15ms

String number: 42000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 16ms

String number: 43000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 15ms

String number: 44000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 15ms

String number: 45000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 16ms

String number: 46000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 47000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 48000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 32ms

String number: 49000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 15ms

String number: 50000

StringBuffer Takes Time: 31ms

StringBuilder Takes Time: 15ms

String number: 51000

StringBuffer Takes Time: 31ms

StringBuilder Takes Time: 31ms

String number: 52000

StringBuffer Takes Time: 31ms

StringBuilder Takes Time: 15ms

String number: 53000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 15ms

String number: 54000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 15ms

String number: 55000

StringBuffer Takes Time: 31ms

StringBuilder Takes Time: 16ms

String number: 56000

StringBuffer Takes Time: 31ms

StringBuilder Takes Time: 16ms

String number: 57000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 16ms

String number: 58000

StringBuffer Takes Time: 32ms

StringBuilder Takes Time: 15ms

String number: 59000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 60000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 16ms

String number: 61000

StringBuffer Takes Time: 32ms

StringBuilder Takes Time: 15ms

String number: 62000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 15ms

String number: 63000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 31ms

String number: 64000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 65000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 16ms

String number: 66000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 16ms

String number: 67000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 15ms

String number: 68000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 16ms

String number: 69000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 70000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 47ms

String number: 71000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 47ms

String number: 72000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 32ms

String number: 73000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 46ms

String number: 74000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 75000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 32ms

String number: 76000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 31ms

String number: 77000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 32ms

String number: 78000

StringBuffer Takes Time: 31ms

StringBuilder Takes Time: 31ms

String number: 79000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 80000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 16ms

String number: 81000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 31ms

String number: 82000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 83000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 84000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 85000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 46ms

String number: 86000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 63ms

String number: 87000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 0ms

String number: 88000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 47ms

String number: 89000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 90000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 91000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 92000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 15ms

String number: 93000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 15ms

String number: 94000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 15ms

String number: 95000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 0ms

String number: 96000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 47ms

String number: 97000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 0ms

String number: 98000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 99000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 16ms

String number: 100000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 94ms

下面是使用了 -Client -Xms256M -Xmx256M参数情况下的测试结果：

String number: 1000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 2000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 3000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 4000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 5000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 16ms

String number: 6000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 16ms

String number: 7000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 16ms

String number: 8000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 15ms

String number: 9000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 10000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 0ms

String number: 11000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 12000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 13000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 16ms

String number: 14000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 15000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 16000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 17000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 16ms

String number: 18000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 0ms

String number: 19000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 16ms

String number: 20000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 0ms

String number: 21000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 16ms

String number: 22000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 0ms

String number: 23000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 0ms

String number: 24000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 16ms

String number: 25000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 0ms

String number: 26000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 0ms

String number: 27000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 15ms

String number: 28000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 15ms

String number: 29000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 0ms

String number: 30000

StringBuffer Takes Time: 31ms

StringBuilder Takes Time: 0ms

String number: 31000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 0ms

String number: 32000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 0ms

String number: 33000

StringBuffer Takes Time: 31ms

StringBuilder Takes Time: 0ms

String number: 34000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 16ms

String number: 35000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 0ms

String number: 36000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 16ms

String number: 37000

StringBuffer Takes Time: 31ms

StringBuilder Takes Time: 0ms

String number: 38000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 16ms

String number: 39000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 40000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 16ms

String number: 41000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 15ms

String number: 42000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 43000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 16ms

String number: 44000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 16ms

String number: 45000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 15ms

String number: 46000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 31ms

String number: 47000

StringBuffer Takes Time: 31ms

StringBuilder Takes Time: 15ms

String number: 48000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 15ms

String number: 49000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 0ms

String number: 50000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 16ms

String number: 51000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 31ms

String number: 52000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 16ms

String number: 53000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 15ms

String number: 54000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 16ms

String number: 55000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 62ms

String number: 56000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 63ms

String number: 57000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 63ms

String number: 58000

StringBuffer Takes Time: 32ms

StringBuilder Takes Time: 62ms

String number: 59000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 47ms

String number: 60000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 47ms

String number: 61000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 63ms

String number: 62000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 78ms

String number: 63000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 78ms

String number: 64000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 94ms

String number: 65000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 62ms

String number: 66000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 78ms

String number: 67000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 78ms

String number: 68000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 78ms

String number: 69000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 78ms

String number: 70000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 78ms

String number: 71000

StringBuffer Takes Time: 0ms

StringBuilder Takes Time: 78ms

String number: 72000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 78ms

String number: 73000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 62ms

String number: 74000

StringBuffer Takes Time: 31ms

StringBuilder Takes Time: 78ms

String number: 75000

StringBuffer Takes Time: 15ms

StringBuilder Takes Time: 78ms

String number: 76000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 78ms

String number: 77000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 62ms

String number: 78000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 62ms

String number: 79000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 63ms

String number: 80000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 47ms

String number: 81000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 63ms

String number: 82000

StringBuffer Takes Time: 16ms

StringBuilder Takes Time: 78ms

String number: 83000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 78ms

String number: 84000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 63ms

String number: 85000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 62ms

String number: 86000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 62ms

String number: 87000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 78ms

String number: 88000

StringBuffer Takes Time: 47ms

StringBuilder Takes Time: 62ms

String number: 89000

StringBuffer Takes Time: 46ms

StringBuilder Takes Time: 79ms

String number: 90000

StringBuffer Takes Time: 94ms

StringBuilder Takes Time: 15ms

String number: 91000

StringBuffer Takes Time: 94ms

StringBuilder Takes Time: 15ms

String number: 92000

StringBuffer Takes Time: 94ms

StringBuilder Takes Time: 15ms

String number: 93000

StringBuffer Takes Time: 78ms

StringBuilder Takes Time: 0ms

String number: 94000

StringBuffer Takes Time: 93ms

StringBuilder Takes Time: 16ms

String number: 95000

StringBuffer Takes Time: 110ms

StringBuilder Takes Time: 0ms

String number: 96000

StringBuffer Takes Time: 94ms

StringBuilder Takes Time: 0ms

String number: 97000

StringBuffer Takes Time: 78ms

StringBuilder Takes Time: 15ms

String number: 98000

StringBuffer Takes Time: 78ms

StringBuilder Takes Time: 16ms

String number: 99000

StringBuffer Takes Time: 94ms

StringBuilder Takes Time: 15ms

String number: 100000

StringBuffer Takes Time: 94ms

StringBuilder Takes Time: 31ms

测试结果概述：

一。对于使用了-Server参数的测试，我们可以看出以下结果：

1。在35000以前，结果是不确定的，也就是说，交替出现了某方为0的结果。

2。从35000到69000，基本是交替领先，领先次数基本是平局。

3。从70000到100000，StringBuffer领先于StringBuilder的比例是22:8。

结论，在这样的测试环境下，StringBuffer的总体表现要比StringBuilder强！

二。对于使用了-Client参数的测试，我们可以看出以下结果：

1。在50000以前，结果是不确定的，也就是说，交替出现了某方为0的结果。

2。从50000到89000，StringBuffer领先于StringBuilder的比例是1:36

3。从90000到100000，StringBuilder领先于StringBuffer的比例是11:0。

结论：本组测试的101组数据中，前五十组可以认为比较失真，后面的五十组StringBuilder领先于StringBuffer的比例是12:36，而且是只有最后的十一组才体现出StringBuilder的优势，因此我们可以得出结论：只有在非常大的字符串数组情况下，StringBuilder的表现才领先于StringBuffer，否则并不占优势。

注：以上测试是在一台运行Windows XP Pro+SP2, 512M内存，Java 1.5，JBuilder 2005 Enterprise的机器上得出的。

全看分页树展 · 主题跟帖

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    😉你试着再加个-Xms256M，看看结果如何？老兵帅客字808 2004-10-05 12:03:36

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