Method selection and performance analysis of Java string splicing

Method Selection of String concatenation

When stitching a static string, use the + as much as possible, because the compiler usually optimizes it, such as:

String test = "This" + "is" + "a" + "test" + "string"

The compiler will treat it as:

String test = "This is a test string"

When stitching dynamic strings, try to use or, as much as possible StringBuffer StringBuilder , to append reduce the construction of too many temporary string objects.

Test code: (as amended in Appendix 1)

1  Public classteststring {2    3      Public voidTestplus () {4String s = "";5         LongTS =System.currenttimemillis ();6          for(inti = 0; I < 10000; i++) {7s = s +string.valueof (i);8         }9         Longref=System.currenttimemillis ();TenSYSTEM.OUT.PRINTLN ("+ Cost {} MS" + (TE-ts)); One     } A      -      Public voidTestconcat () { -String s = ""; the         LongTS =System.currenttimemillis (); -          for(inti = 0; I < 10000; i++) { -s =S.concat (string.valueof (i)); -         } +         LongTe =System.currenttimemillis (); -System.out.println ("concat cost {} MS" + (TE-ts)); +     } A  at      -      Public voidTeststringbuffer () { -StringBuffer SB =NewStringBuffer (); -         LongTS =System.currenttimemillis (); -          for(inti = 0; I < 10000; i++) { - Sb.append (string.valueof (i)); in         } - sb.tostring (); to         LongTe =System.currenttimemillis (); +System.out.println ("StringBuffer Cost {} MS" + (TE-ts)); -     } the      *      Public voidTeststringbuilder () { $StringBuilder SB =NewStringBuilder ();Panax Notoginseng         LongTS =System.currenttimemillis (); -          for(inti = 0; I < 100000; i++) { the Sb.append (string.valueof (i)); +         } A sb.tostring (); the         Longref=System.currenttimemillis (); +System.out.println ("StringBuilder Cost {} MS" + (TE-ts)); -     } $      $      Public Static voidMain (string[] args) { -TestString A =Newteststring (); - A.testconcat (); the A.testplus (); - A.teststringbuffer ();Wuyi A.teststringbuilder (); the     } -}

Operation Result:

Concat Cost {} MS 113
+ Cost {} MS 195
StringBuffer Cost {} MS 2
StringBuilder Cost {} MS 9

Appendix:

1 Java 5 String Stitching mode performance Comparison http://blog.csdn.net/kimsoft/article/details/3353849

2 Java Performance Optimization String article http://www.ibm.com/developerworks/cn/java/j-lo-optmizestring/

Method selection and performance analysis of Java string splicing