Java课件第二章补充 字符串.ppt

《Java课件第二章补充 字符串.ppt》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、IConstructingaStringChapter2TheStringClassIIStringMethods1TheStringClassConstructingaString:ObtainingStringlengthandRetrievingIndividualCharactersinastringStringStringConcatenation(concat)Substrings(substring(index),substring(start,end))Comparisons(equals,compa

2、reTo)StringConversionsFindingaCharacteroraSubstringinaStringConversionsbetweenStringsandArraysConvertingCharactersandNumericValuestoStrings2ConstructingStringsFormat:StringnewString=newString(stringLiteral);Stringmessage=“stringLiteral";Example:Stringmessage=ne

3、wString(“Hello");Stringmessage="WelcometoJava";3StorageStringpool&stack&heapStringpool（字符串池）:JVMhasaStringpool,itsavesalotofStringobjectsthatcreatedbyshorthandinitializer.DatasharingStack（栈）:Storeprimitivedata（char、byte、short、int、long、float、double、boolean）andco

4、nstructor.Datasharing.heap（堆）：StoreObject.4Stringstr=newString("abc");DifferencebetweennewandshorthandinitializerQuestion:HowmanyStringobjectsarecreated?TwoConstructor:public String(String original) {//other code ...}Note:TheparameterisaStringobject5String a="a

5、bc";Stringb="abc";DifferencebetweennewandshorthandinitializerQuestion:HowmanyStringobjectsarecreated?One6Anewobjectiscreatedifyouusethenewoperator.Ifyouusethestringinitializer,nonewobjectiscreatediftheinternedobjectisalreadycreated.Note7StringsAreImmutableAStri

6、ngobjectisimmutable;itscontentscannotbechanged.DoesthefollowingcodechangethecontentsofthestringStrings="Java";s="HTML";？8s:StringStringobjectfor“Java”0x1245sTraceCodeStrings="Java";s="HTML";ContentscannotbechangedAfterexecutings=“java”;s:StringStringobjectfor“J

7、ava”0x1245sAfterexecutings=“HTML”;s:StringStringobjectfor“HTML”×9CanonicalStrings（规范字符串）canonicalstring:iftwoStringobjectswerecreatedwiththesamestringliteralusingtheshorthandinitializer,thentheJVMstorestheminthesameobject.Thisstringliteraliscalledcanonicalstrin

8、g.improveefficiencyandsavememoryUsingStringobject’sinternmethodtoreturnacanonicalstring10intern:publicnativeStringintern()Returnsacanonicalrepresentationforthestringobject.I