input output in javajava中的输入输出

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1、Input/OutputinJavaInput/OutputinJavacanbedoneusingthekeyboardandscreen,usingfiles,orsomecombinationofthesemethods.Inputtypedatthekeyboardandoutputdisplayedonthescreenareoftenreferredtoasconsoleinput/output.Interactiveinput/outputusingthekeyboardandscreenisthedefaultwayofdoinginput/output

2、injGRASP.Itisalsopossibletouseadialogboxtogetinputfromtheuserandtodisplayamessage.Javareferstotheseasaninputdialogandmessagedialogrespectively.Anobjectisalwaysneededtoperformaninput/outputoperationinJava.DisplayOutput[standardoutput]·DisplayingscreenoutputinJavaisdoneusingtheSystem.outob

3、ject.YoudonotneedtocreatetheSystem.outobject.ItisalwaysavailableforyouuseinaJavaprogram.Thereare3methodsthatcanbeusedtodisplayoutput:print(),printf(),andprintln().oTheprint()methodisoftenusedtodisplayapromptoraportionofaline.Itdoesnotmovethecursortothebeginningofanewlineautomatically.oTh

4、eprintln()methoddisplaysoutputexactlythesameastheprint()methodexceptthatitwillalwaysmovethecursortothebeginningofanewlineasthelastactionitperforms.oTheprintf()methodisusedtooutputformattedtextandnumbers.Liketheprint()method,Itdoesnotmovethecursortothebeginningofanewlineautomatically.Keyb

5、oardInput[standardinput]·AcceptingkeyboardinputinJavaisdoneusingaScannerobject.ThereisaSystem.inobjectinJavathatcanbeusedtogetinputinJava,butitisnotveryfunctional.Instead,JavaprogrammersusuallyprefertouseaScannerobjectthathasbeen"mapped"totheSystem.inobject.TheSystem.inobject(liketheSyst

6、em.outobject)alreadyexistsandisavailableforuse.However,youmustcreateaScannerobject.OnceyouhavecreatedaScannerobjectand"mapped"ittotheSystem.inobjectyoucanusethefollowingmethodstotestforandgetinput.InputalwayscomesintoaJavaprogramasastringofcharacters(JavaStringtype).Therearemethodsthatca

7、nbeusedtoconverttheStringtoacharacter,anintegernumber,afloating-pointnumber,etc.HerearecommonlyusedScannermethods:hasNext()//issomethingavailabletoread?Returnstrueorfalse.nextInt()//getanintnextFloat()//getafloatnextDouble()//getadoublenextBoolean()//getabooleanvalue(true