java面向?qū)ο蟮?天接口

11天面向?qū)Φ?章接與定義類的classinterface定義接口所在的仍為.java文件，雖然時(shí)使用的為interface關(guān)鍵字的編譯后仍然會(huì)產(chǎn)生.class文publicpublicinterface抽象方法抽象方法抽象方法}implements。classclassimplements}staticfinal關(guān)鍵字interfaceDemointerfaceDemo定義一個(gè)名稱為DemopublicstaticfinalintNUM3NUM的值不能改 void void}//定義子類去覆蓋接口中的方法。類與接口之間的關(guān)系是通過(guò)implementsclassDemoImplimplementsDemo{//子類實(shí)現(xiàn)Demo接口。publicvoidshow1(){}publicvoid}接口最重要的體現(xiàn)：解決多繼承的弊端。將多繼承這種機(jī)制在javainterfaceinterface{void}interfaceinterface{void}classZiimplementsFu1,Fu2{publicvoidshow1(){}publicvoid}classFuclassFupublicvoid}interfaceInter void}classZiextendsFuimplementsInter{publicvoidshow1(){}}interfaceinterfacevoid}}interfaceFu2{voidshow1();}interfaceFu3{voidshow2();}interfaceZiextendsFu1,Fu2,Fu3{voidshow3();}interfaceinterface緝毒}void緝毒class犬科 void吃飯 void吼叫}//class緝毒犬extends犬科implements緝毒publicvoid緝毒}void吃飯}void吼叫}}class緝毒豬implements緝毒{publicvoid緝毒(){}}抽象類為部分方法提供實(shí)現(xiàn),避免子類重復(fù)實(shí)現(xiàn)這些方法,提高代碼重用性;接口只能包含抽象方法;Java第2章多Java作為面向?qū)ο蟮恼Z(yǔ)言同樣可以描述一個(gè)事物的多種形態(tài)如Student類繼承了類一個(gè)Student的對(duì)象便既是Student，又是。Java中多態(tài)的代碼體現(xiàn)在一個(gè)子類對(duì)象(實(shí)現(xiàn)類對(duì)象)既可以給這個(gè)子類(實(shí)現(xiàn)類對(duì)象)變量賦如Student類可以為類的子類。那么一個(gè)Student對(duì)象既可以賦值給一個(gè)Student類型 父類類型變量名new子類類型父類類型變量名new子類類型父類父類new子類();如classFu{}classZiextendsFuFuf=new抽象類抽象類變量名=new抽象類子類(); classFu{ void}classZiextendsFupublicvoidmethod(){publicvoidmethod(){}}Fufu=new接口接口new接口實(shí)現(xiàn)類();如：interfaceFu{ void}classZiimplementsFu{publicvoidmethod(){}}Fufu=new p1=newp2=newp1.workp1會(huì)調(diào)用Student類中重寫的work方p2.workp2會(huì)調(diào)用Teacher p1=newp2=newp1.workp1會(huì)調(diào)用Student類中重寫的work方p2.workp2會(huì)調(diào)用Teacher類中重寫的work方classclassFuintnum=}classZiextendsFu{intnum=5;}classDemopublicstaticvoidmain(String[]args){Fuf=newZi();Ziz=newZi();}}classFuclassFuintnum=4;voidshow()System.out.println("Fushow}}classZiextendsFu{intnum=5;voidshow()System.out.println("Zishow}}classDemopublicstaticvoidmain(String[]args){Fuf=newZi();}}instanceofinstanceof關(guān)鍵字來(lái)判斷某個(gè)對(duì)象是否屬于某種數(shù)據(jù)類型。如學(xué)生的對(duì)象屬于學(xué)booleanbooleanb=對(duì)象instanceof數(shù)據(jù)類型如p1p1newStudentbooleanbooleanflagp1instanceofStudent;flag結(jié)果為booleanflag2p2instanceofAnimal;flag結(jié)果為多態(tài)父類類父類類型變量名new子類類型如 p=new 子類類型子類類型子類類型父類類型的變量如:StudentstuStudentp;//變量p實(shí)際上指向Student對(duì)//描述動(dòng)物類，并抽取共性eat方classAnimalvoid}描述狗類，繼承動(dòng)物類，重寫eat方法，增加lookHome方classDogextendsAnimalvoideat()//描述動(dòng)物類，并抽取共性eat方classAnimalvoid}描述狗類，繼承動(dòng)物類，重寫eat方法，增加lookHome方classDogextendsAnimalvoideat()}voidlookHome(){}}//描述貓類，繼承動(dòng)物類，重寫eat方法，增加 classCatextendsAnimalvoidvoideat()}voidcat ouse(){}}publicclassTestpublicstaticvoidmain(String[]args)Animala=newDog();//多態(tài)形式，創(chuàng)建一個(gè)狗對(duì)象a.eat調(diào)用對(duì)象中的方法，會(huì)執(zhí)行狗類中的eat方法//a.lookHome();//使用Dog類特有的方法，需要向 為了使用狗類的lookHome//向 if(ainstanceofDog判斷當(dāng)前對(duì)象是否是Dog類型}Dogd=(Dog)a;//向下d.lookHome();//調(diào)用狗類的lookHome方法}}如：AnimalanewDog();如：AnimalanewDog();如：DogdDoga;如：DogdDoga;弊端是需要面對(duì)具體的子類對(duì)象在向下時(shí)容易發(fā)生ClassCastException類型轉(zhuǎn) 如：if(!ainstanceof class畢姥爺void講課} (){ }} //class畢老師extendsvoid講課}void看 (){ }}publicclassTestpublicstaticvoidmain(String[]args)多態(tài)形畢姥爺anew畢老師向講課功 //當(dāng)要調(diào)用畢老師特有的看 畢老師b=(畢老師)a;//向下 }}}第3章筆記本電腦案USBUSBUSBUSB設(shè)USB規(guī)格的設(shè)備都可以。鼠標(biāo)和鍵盤要想能在電腦上使用，那么鼠USB規(guī)范，不然鼠標(biāo)和鍵盤的生產(chǎn)出來(lái)無(wú)法使用USB鼠標(biāo)、USBinterfaceinterfaceUSBvoidopen();// voidvoidclose}classclassMouseimplementsUSB{publicvoidopen(){}publicvoidclose(){}}classclassKeyBoardimplementsUSB{publicvoidopen(){}publicvoidclose(){}}classclassNoteBookpublicvoidrun(){}//筆記本使用usb設(shè)備，這時(shí)當(dāng)筆記本對(duì)象調(diào)用這個(gè)功能時(shí)，必須給其傳遞一個(gè)符合USB規(guī)則的設(shè)publicvoiduseUSB(USBusb)判斷是否有USB設(shè)備ifusbnull}}publicvoidshutDown(){}}}publicpublicclassTestpublicstaticvoidmain(String[]args)NoteBooknb=new創(chuàng)建鼠標(biāo)實(shí)體對(duì)Mousem=new創(chuàng)建鍵盤實(shí)體對(duì)KeyBoardkb=new}}第4章總interfaceclassDemoimplementsInter{}3,接口不能直接創(chuàng)建對(duì)象finalpublicstaticc