Java String concatenation and Performance

Use

Concatenation operator (+)

String Concat method-Concat (string Str)

Stringbuffer append method-append (string Str)

Stringbuilder append method-append (string Str)

Perform performance tests.

 

Environment: win7 32-bit, CPU dual-core 2.5 GHz, 2 GB memory.

The test code is as follows:

Private final static int OUTER_ITERATION = 10; <br/> private final static int INNER_ITERATION = 50000; </p> <p>/** <br/> * @ param args <br/> */<br/> public static void main (String [] args) {<br/> String addTestStr = ""; <br/> String concatTestStr = ""; <br/> StringBuffer concatTestSb = null; <br/> StringBuilder concatTestSbu = null; </p> <p> for (int outerIndex = 0; outerIndex <OUTER_ITERATION; outerIndex ++) {<br/> StopWatch stopWatch = new LoggingStopWatch ("StringAddConcat "); <br/> addTestStr = ""; <br/> for (int innerIndex = 0; innerIndex <INNER_ITERATION; innerIndex ++) <br/> addTestStr + = "*"; <br/> stopWatch. stop (); <br/>}</p> <p> for (int outerIndex = 0; outerIndex <OUTER_ITERATION; outerIndex ++) {<br/> StopWatch stopWatch = new LoggingStopWatch ("StringConcat"); <br/> concatTestStr = ""; <br/> for (int innerIndex = 0; innerIndex <INNER_ITERATION; innerIndex ++) <br/> concatTestStr. concat ("*"); <br/> stopWatch. stop (); <br/>}</p> <p> for (int outerIndex = 0; outerIndex <OUTER_ITERATION; outerIndex ++) {<br/> StopWatch stopWatch = new LoggingStopWatch ("StringBufferConcat"); <br/> concatTestSb = new StringBuffer (); <br/> for (int innerIndex = 0; innerIndex <INNER_ITERATION; innerIndex ++) <br/> concatTestSb. append ("*"); <br/> stopWatch. stop (); <br/>}</p> <p> for (int outerIndex = 0; outerIndex <OUTER_ITERATION; outerIndex ++) {<br/> StopWatch stopWatch = new LoggingStopWatch ("StringBuilderConcat"); <br/> concatTestSbu = new StringBuilder (); <br/> for (int innerIndex = 0; innerIndex <INNER_ITERATION; innerIndex ++) <br/> concatTestSbu. append ("*"); <br/> stopWatch. stop (); <br/>}</p> <p>}

 

Test results:
Performance Statistics 06:16:00-06:16:30

Tag	MS (avg)	Min	Max	Std Dev	Count
Stringaddconcat	9355.4	7860	10046	547.7	10
Stringbufferconcat	3.5	0	5	2.3	10
Stringbuilderconcat	2.0	0	5	2.4	10
Stringconcat	3.1	0	6	2.5	10