Java程序设计第五章继承、接口和抽象类程序阅读题及答案

1、现有‎publicclassParent{‎publicvoidchange(intx){‎}‎}‎publicclassChildextendsParent{‎／／覆盖父类change方法‎}‎下列哪个声明是正确的覆盖了父类的change方法？‎A.publicvoidchange(intx){}B.protectedvoidchange(intx){}C.publicvoidchange(Strings){}D.publicvoidchange(intx,inty){}正确答案：A2、​classCa{ intnum=1; Ca(intnum){ this.num=num; System.out.print(this.num); }}classCbextendsCa{​​intnum=2; Cb(intnum){ this.num=num;System.out.print(num);​​ } publicstaticvoidmain(String[]args){ Caa=newCb(5); }}​​运行代码，程序输出结果为：A.52B.51C.编译报错D.15正确答案：C3、‏下面关于继承的叙述正确的是（）A.Java类中只允许单一继承B.Java中一个类不能同时继承一个类和实现一个接口C.Java中一个类只能实现一个接口D.Java中一个类可继承于多个类正确答案：A4、‌给定下列程序，请选出正确结果。‌classCat{‌Cat(intc){‌System.out.print("cat"+c+"");‌}‌}‏‌classSubCatextendsCat{‌SubCat(intc){‌super(5);‌System.out.print("cable");‏‌}‏‌SubCat(){‌this(4)；‌}‏‌publicstaticvoidmain(String[]args){‌SubCats=newSubCat();‌}‌}‏A.cablecat5B.cableC.cat5D.cat5cable正确答案：D5、‌下列程序的输出是（）。‌classOther{‌publicOther(){‌System.out.print("Other!");‌ }‌}‏‌publicclassDriver1extendsOther{‌publicstaticvoidmain(String[]args){‌newDriver1();‌newOther();‌}‌}‏A.Other!Other!B.Other!C.Other!Other!Other!D.编译出错正确答案：A6、​请选出以下程序的输出结果​classA{​ publicvoidfunc1(){​ System.out.println("Afunc1iscalling");​ }​​ publicvoidfunc2(){​ func1();​ }​}​​classBextendsA{​ publicvoidfunc1(){​ System.out.println("Bfunc1iscalling");​ }​ publicvoidfunc3(){​ System.out.println("Bfunc3iscalling");​ }​}​​classC{​ publicstaticvoidmain(String[]args){​Aa=newB();​a.func1();​a.func2();​a.func3();​ } ​}Afunc1iscallingBfunc3iscallingBfunc1iscallingBfunc3iscallingAfunc1iscallingAfunc1iscallingBfunc3iscallingD.编译错误正确答案：D7、​请选出以下程序的输出结果​publicclassChildextendsPeople{​ Peoplefather;​​ publicChild(Stringname){​ System.out.print(3);​ =name;​ father=newPeople(name+":F");​ }​ publicChild(){​ System.out.print(4);​ }​ publicstaticvoidmain(String[]args){​ newChild("Alice");​ }​}​​classPeople{​ Stringname;​​ publicPeople(){​ System.out.print(1);​ }​ publicPeople(Stringname){​ System.out.print(2);​ =name;​ }​}A.123B.132C.32D.312正确答案：B8、‏请选出正确答案‏classParent{‏Stringone,two;‏publicParent(Stringa,Stringb){‏one=a;‏two=b;‏}‏publicvoidprint(){System.out.println(one);}‏}​‏publicclassChildextendsParent{‏publicChild(Stringa,Stringb){‏super(a,b);‏}​‏publicvoidprint(){‏System.out.println(one+"to"+two);‏}​‏publicstaticvoidmain(Stringarg[]){‏Parentp=newParent("south","north");‏Parentt=newChild("east","west");‏p.print();‏t.print();‏}‏}​southtonortheasttowestsoutheasttowestCauseerrorduringcompilation.D.southtonortheast正确答案：B9、‎请选择正确的输出结果‎‎classGuy{‎ publicGuy(){‎ System.out.print("111,");‎ }‎}‎‎classCowboyextendsGuy{‎ publicCowboy(){‎ System.out.print("222,");‎ }‎}‎‎classWranglerextendsCowboy{‎ publicWrangler(){‎ System.out.print("333,");‎ }‎}‎publicclassGreeting2{‎ publicstaticvoidmain(String[]args){‎ Guyg1=newGuy();‎ Guyg2=newCowboy();‎ Guyg3=newWrangler();‎ }‎}‎A.编译错误B.111,111,222,111,222,333,C.111,111,222,222,333,D.111,222,333,正确答案：B10、‏给定以下程序‏classPencil{‏ publicvoidwrite(Stringcontent){‏ System.out.println("Write"+content);‏ }‏}‏‏classRubberPencilextendsPencil{‏ publicvoidwrite(Stringcontent){‏ System.out.println("RubberWrite"+content)；‏ }‏‏publicv