C/C++字符串拼接测试运行结果：

 

Release version.

TEST_TIME: 90000

C language memcpy append Used: 0 ms.

string length: 630000

std::string += operator Used: 15 ms.

string length: 630000

std::string append Used: 16 ms.

string length: 630000

std::ostringstream << Used: 16 ms.

string length: 630000

capacity: 630015

size: 0

hava resize(PREALLOCATE_SIZE) std::string += operator Used: 0 ms.

string length: 630000

MFC CString append Used: 63 ms.

string length: 630000

MFC CString operator append Used: 62 ms.

string length: 630000

c string function strcat: Used: 32203 ms.

string length: 630000

---------Statistics informations(sorting ascendent)-------

 

sort order: 1

item: C language memcpy append

used: 0 ms.

 

sort order: 2

item: hava resize(PREALLOCATE_SIZE) std::string += operator

used: 0 ms.

 

sort order: 3

item: std::string += operator

used: 15 ms.

 

sort order: 4

item: std::string append

used: 16 ms.

 

sort order: 5

item: std::ostringstream <<

used: 16 ms.

 

sort order: 6

item: MFC CString operator append

used: 62 ms.

 

sort order: 7

item: MFC CString append

used: 63 ms.

 

sort order: 8

item: c string function strcat:

used: 32203 ms.

 

----------------------------------------------------------

Press any key to continue . . .

Java的测试代码段:

void testJavaStringPerformance() {

final int TEST_TIMES = 90000;

       //String

       String str = new String();

 

       System.out.println("The testing is running, please wait...");

       long start = System.currentTimeMillis();       

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

              str += "cppmule";

       }

       long strUsed = System.currentTimeMillis() - start;

       System.out.println("strUsed: " + strUsed + " ms.");

      

//StringBuffer

       start = 0;

       StringBuffer strBuffer = new StringBuffer();

       start = System.currentTimeMillis();

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

              strBuffer.append("cppmule");

       }

       long strBufferUsed = System.currentTimeMillis() - start;

       System.out.println("StringBuffer append: " + strBufferUsed + " ms.");

      

       //StringBuilder

       start = 0;

       StringBuilder strBuilder = new StringBuilder();

       start = System.currentTimeMillis();

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

              strBuilder.append("cppmule");

       }

       long strBuilderUsed = System.currentTimeMillis() - start;

       System.out.println("StringBuilder append: " + strBuilderUsed + " ms.");

       System.out.println("Times: " + TEST_TIMES);

}

Java字符串拼接运行结果:

 

The testing is running, please wait...

strUsed: 443141 ms.

StringBuffer append: 15 ms.

StringBuilder append: 31 ms.

Times: 90000

 

Author:

By: cppmule

Email: cppmule@gmail.com

 

 

 

 

StringBuffer  竟然比 StringBuilder快一倍。这是怎么个情况？

StringBuffer可是线程安全的，虽然程序没用到多线程，但怎么也比StringBuilder要多耗一点时间吧。。

这个好像没有什么可比性。除掉调式信息+server模式再试下！

StringBuffer append: 48 ms.
StringBuilder append: 14 ms.
Times: 90000

The testing is running, please wait...
strUsed: 57125 ms.
StringBuffer append: 16 ms.
StringBuilder append: 0 ms.
Times: 90000

你直接用加号 +++++ 都比StringBuffer 快 stringbuffer是线程安全的吧

我对你测试结果标识怀疑.你等等 啊

我记得+也挺快的么..估计写道for循环里..jdk不做优化了..

“记得”就是感觉吧

打开class文件看看+的实现就知道他们之间的区别了！

区别：1 对象创建个数 2 线程安全

偶测过，stringbuffer不可能有stringbuilder快的，在7次拼装一下+都比stringbuffer快。