java面向对象考题和答案

1.下面代码的输出结果是:publicclassMain{publicstaticvoidmain(String[]args){intn=100;intm=200;System.out.println(f(n,m));System.out.println(n);}publicstaticintf(intm,intn){n=m+n;returnn;}}A.300300B.100100C.300100D.1003002.程序执行的结果是：publicclassTest{publicstaticvoidmain(String[]args){intx=6;Testp=newTest();p.doStuff(x);System.out.println(main：x=+x);}voiddoStuff(intx){System.out.println(doStuff：x=+x++);}}A.doStuff：x=7main：x=7B.doStuff：x=7main：x=6C.doStuff：x=6main：x=7D.doStuff：x=6main：x=63.下列关于JVM的内存结构描述正确的是：A.类的各种信息在方法区中保存B.堆用于存放程序运行过程当中所有的局部变量C.栈用于存储使用new关键字创建的对象D.数组属于JVM的内存结构4.下列代码的输出结果是：publicclassTest{publicvoidprint(charc){System.out.println(c);}publicvoidprint(inti){System.out.println(i);}publicvoidprint(doubled){System.out.println(d);}publicvoidprint(Strings){System.out.println(s);}publicstaticvoidmain(String[]args){Testtest=newTest();test.print('5');}}A.cB.iC.dD.s5.程序执行的结果是：publicclassTest{Stringname=Tom;publicTest(Stringname){name=name;}publicstaticvoidmain(String[]args){Testt=newTest(Jack);System.out.println(t.name);}}A.nullB.TomC.JackD.6.关于构造方法，下列说法错误的是:A.构造方法不可以进行方法重写B.构造方法用来实例化一个新的对象C.构造方法具有和类名相同的名称D.构造方法不返回任何数据类型7.关于Java中继承的特点，下列说法正确的是:A.使类的定义复杂化B.Java只支持单继承，不可多继承，但可以通过实现接口来达到多继承的目的C.子类继承父类的所有成员变量和方法，包括父类的构造方法D.不可以多层继承，即一个类不可以继承另一个类的子类8.下列代码运行的结果是：classFoo{publicinta;publicFoo(){a=3;}publicvoidaddFive(){a+=5;}}classBarextendsFoo{publicinta;publicBar(){a=8;}publicvoidaddFive(){this.a+=5;}}publicclassTestFoo{publicstaticvoidmain(String[]args){Foofoo=newBar();foo.addFive();System.out.println(Value:+foo.a);}}A.Value:3B.Value:8C.Value:13D.Value:189.下列代码编译和运行的结果是：classPerson{Stringname=Noname;publicPerson(Stringnm){name=nm;}}classEmployeeextendsPerson{StringempID=0000;publicEmployee(Stringid){empID=id;}}publicclassEmployeeTest{publicstaticvoidmain(String[]args){Employeee=newEmployee(4321);System.out.println(e.empID);}}A.输出：0000B.输出：4321C.代码publicEmployee(Stringid){行，出现编译错误D.抛出运行时异常10.下列代码的运行结果是：publicclassAnimal{publicStringnoise(){returnpeep;}publicstaticvoidmain(String[]args){Animalanimal=newDog();Catcat=(Cat)animal;System.out.println(cat.noise());}}classDogextendsAnimal{publicStringnoise(){returnbark;}}classCatextendsAnimal{publicStringnoise(){returnmeow;}}A.peepB.barkC.meowD.抛出运行时异常11.下列代码编译和运行的结果是：publicclassA{publicvoidstart(){System.out.println(TestA);}}publicclassBextendsA{publicvoidstart(){System.out.println(TestB);}publicstaticvoidmain(String[]args){((A)newB()).start();}}A.输出：TestAB.输出：TestBC.输出：TestATestBD.编译错误12.请看下列代码：classOne{voidfoo(){}}classTwoextendsOne{//insertmethodhere}下列选项中的代码，放置在插入代码处无编译错误的是：A.intfoo(){/*morecodehere*/}B.protectedvoidfoo(){/*morecodehere*/}C.publicvoidfoo(){/*morecodehere*/}D.privatevoidfoo(){/*morecodehere*/}13.下列选项中，不属于Java的访问修饰符的是：A.privateB.protectedC.friendlyD.public14.下列代码的输出结果是：classFoo{privateintx;publicFoo(intx){this.x=x;}publicvoidsetX(intx){this.x=x;}publicintgetX(){returnx;}}publicclassGamma{staticFoofooBar(Foofoo){foo=newFoo(100);returnfoo;}publicstaticvoidmain(String[]args){Foofoo=newFoo(300);System.out.print(foo.getX()+-);FoofooFoo=fooBar(foo);System.out.print(foo.getX()+-);System.out.print(fooFoo.getX()+-);foo=fooBar(fooFoo);System.out.print(foo.getX()+-);System.out.print(fooFoo.getX());}}A.300-100-100-100-100B.300-300-100-100-100C.300-300-300-100-100D.300-300-300-300-10015.下列代码运行的结果是：publicclassBase{publicstaticfinalStringFOO=foo;16.classSubextendsBase{publicstaticfinalStringFOO=bar;}publicstaticvoidmain(String[]args){Baseb=newBase();Subs=newSub();System.out.print(Base.FOO);System.out.print(Sub.FOO);System.out.print(b.FOO);System.out.print(s.FOO);System.out.print(((Base)s).FOO);}}A.foofoofoofoofooB.foobarfoobarbarC.foobarfoofoofooD.foobarfoobarfoo16.关于下列代码说法正确的是：publicclassItemTest{privatefinalintid;publicItemTest(intid){this.id=id;}publicvoidupdateId(intnewId){id=newId;}publicstaticvoidmain(String[]args){ItemTestfa=newItemTest(42);fa.updateId(69);System.out.println(fa.id);}}A.编译错误B.运行时抛出异常C.运行后，fa对象属性id的值没有改变，应然是42D.运行后，fa对象属性id的值改变成新的值6917.请看下列代码编译和运行的结果是：publicclassStudent{privateStringname=sun;publicstaticvoidmain(String[]args){Student[]students=newStudent[2];System.out.println(students[0].name);System.out.println(students.length);}}A.sun2B.null2C.null1D.运行时抛出NullPointerException异常18.下列代码的输出结果是：abstractclassVehicle{publicintspeed(){return0;}}classCarextendsVehicle{publicintspeed(){return60;}}classRaceCarextendsCar{publicintspeed(){return150;}}publicclassTestCar{publicstaticvoidmain(String[]args){RaceCarracer=newRaceCar();Carcar=newRaceCar();Vehiclevehicle=newRaceCar();System.out.println(racer.speed()+,+car.speed()+,+vehicle.speed());}}A.0,0,0B.150,60,0C.150,150,150D.抛出运行时异常19.请看下列代码：publicabstractclassEmployee{protectedabstractdoublegetSalesAmount();publicdoublegetCommision(){returngetSalesAmount()*0.15;estA(){}}classSalesextendsEmployee{插入代码}在插入代码处填入的方法正确的是：A.doublegetSalesAmount(){return1230.45;}B.publicdoublegetSalesAmount(){return1230.45;}C.privatedoublegetSalesAmount(){return1230.45;}D.protecteddoublegetSalesAmount(){return1230.45;}20.关于下列代码说法正确