3Java第三单元练习题-常用类

13常用类3.1单项选择题1.设有下面两个赋值语句：a=Integer.parseInt(“12”);b=Integer.valueOf(“12”).intValue();下述说法正确的是（）。A．a是整数类型变量，b是整数类对象。B．a是整数类对象，b是整数类型变量。C．a和b都是整数类对象并且值相等。D．a和b都是整数类型变量并且值相等。2.关于以下代码段的说法正确的是（）1．Strings=abcde;2．StringBuffers1=newStringBuffer(abcde);3．if(s.equals(s1))4．s1=null;5．if(s1.equals(s))6．s=null;A．第1行编译错误，String的构造器必须明确调用B．第3行编译错误，因为s与s1有不同的类型C．编译成功，但执行时在第5行有异常抛出D．编译成功，过程中也没有异常抛出3.已知如下定义：Strings=story;下面哪个语句不是合法的()A．s+=books;B．s=s+100;C．intlen=s.length;D．Stringt=s+“abc”;4.下列程序段执行后的结果是()。Strings=newString(abcdefg);for(inti=0;is.length();i+=2){System.out.print(s.charAt(i));}A．acegB．ACEGC．abcdefgD．abcd5.有整型数组：int[]x={12,35,8,7,2};,则调用方法Arrays.sort(x)后，数组x中的元素值依次是().A．2781235B．1235872C．3512872D．87123526.应用程序的main方法中有以下语句，则输出的结果是()。Strings1=newString(abc);Strings2=newString(abc);booleanb1=s1.equals(s2);2booleanb2=(s1==s2);System.out.print(b1++b2);A．truefalseB．falsetrueC．truetrueD．falsefalse7.应用程序的main方法中有以下语句，则输出的结果是()。Strings=12345#aaa#bbb#67890;intn=s.indexOf(#);intk=s.indexOf(#,n+1);intm=s.indexOf(#,k+1);Strings2=s.substring(m+1);System.out.println(s2);A．123456B．67890C．aaaD．bbb8.应用程序的main方法中有以下语句，则输出的结果是()。Strings=xxxxxxxxxxxxxxx#123#456#zzzzz;intn=s.indexOf(#);intk=s.indexOf(#,n+1);Strings2=s.substring(n+1,k);System.out.println(s2);A)123456B)123C)xxxxxxxxxxxxxxxD)zzzzz9.请说出下列代码的执行结果:Strings=abcd;Strings1=newString(s);if(s==s1)System.out.println(thesame);if(s.equals(s1))System.out.println(equals);A.thesameequalsB.equalsC.thesameD.什么结果都不输出3.2简答题1.String和StringBuffer的区别？3.3程序阅读题1.阅读以下程序，写出输出结果。classAnimal{Animal(){System.out.print(Animal);}}publicclassDogextendsAnimal{Dog(){3System.out.print(Dog);}publicstaticvoidmain(String[]args){Dogsnoppy=newDog();}}2、以下程序的输出结果为_____。publicclassCourse{privateStringcNumber;privateStringcName;privateintcUnit;publicCourse(Stringnumber,Stringname,intunit){cNumber=number;cName=name;cUnit=unit;}publicvoidprintCourseInfo(){System.out.println(课程号:+cNumber+课程名:+cName+学分:+cUnit);}}classCourseTest{publicstaticvoidmain(String[]args){Coursec;c=newCourse(101,ASP,3);c.printCourseInfo();}}3、以下程序的输出结果为_____。publicclassTom{privatefloatweight;privatestaticStringname;publicvoidsetWeight(floatweight){this.weight=weight;}privatevoidout(){System.out.println(name+体重：+weight+斤);4}publicstaticvoidmain(String[]args){Tom.name=汤姆猫;Tomcat=newTom();cat.setWeight(20);cat.out();}}4、以下程序的输出结果__。publicclassFather{Stringname,address,tel;intage;publicFather(Stringname,intage){this.name=name;this.age=age;}voidout(){System.out.print(姓名:+name);System.out.print(年龄:+age);}voidoutOther(){System.out.print(家庭住址:+address);System.out.print(电话:+tel);}}classSonextendsFather{Stringschool;publicSon(Stringname,intage){super(name,age);}voidout(){super.out();super.outOther();System.out.println(学校：+school);}5publicstaticvoidmain(Stringargs[]){Sonson=newSon(Tom,15);son.address=中关村;son.school=八中;son.tel=66123456;son.out();}}5、下列程序的运行结果是______。publicclassMyClass{inta[]={1,2,3,4,5};voidout(){for(intj=0;ja.length;j++)System.out.print(a[j]+);}publicstaticvoidmain(String[]args){MyClassmy=newMyClass();my.out();}}6.写出下面的程序编译、运行后的结果(6分)。publicclassTest{publicstaticvoidmain(Stringargs[]){newStudent(Tom,'m',90,88);newStudent(Jack,'m',66,89);newStudent(Mary,'f',76,86);System.out.println(name\tsex\tchinese\tenglish);Student.print();}}classStudent{protectedStringname;protectedcharsex;protectedintchinese;protectedintenglish;protectedStudentnext;staticStudentlist;Student(Stringname,charsex,intchinese,intenglish){6this.name=name;this.sex=sex;this.chinese=chinese;this.english=english;this.next=list;list=this;}staticvoidprint(){Studentfriend=list;if(friend==null)System.out.println(Thelistisempty.);else{do{System.out.println(friend.toString());friend=friend.next;}while(friend!=null);}}publicStringtoString(){returnnewString(name+\t+sex+\t+chinese+\t+english);}}7.阅读程序，给出结果：//AbstractClassDemo.java源代码如下：abstractclassShape{//定义抽象类Shape和抽象方法displayabstractvoiddisplay();}classCircleextendsShape{voiddisplay(){//实现抽象类的方法System.out.println(Circle);}}classRectangleextendsShape{voiddisplay(){//实现抽象类的方法System.out.println(Rectangle);}}classTriangleextendsShape{voiddisplay(){//实现抽象类的方法System.out.println(Triangle);}}publicclassAbstractClassDemo{publicstaticvoidmain(Stringargs[]){7(newCircle()).display();//定义无名对象来调用对应的display方法(newRectangle()).display();(newTriangle()).display();}}输出结果是?8.按要求填空abstractclassSuperAbstract{voida(){…}abstractvoidb();abstractintc(inti);}interfaceAsSuper{voidx();}abstractclassSubAbstractextendsSuperAbstractimplementsAsSuper{publicvoidb(){…}abstractStringf();}publicclassInheritAbstractextendsSubAbstract{publicvoidx(){…}publicintc(inti){…}publicStringf(){…}publicstaticvoidmain(Stringargs[]){InheritAbstractinstance=newInheritAbstract();instance.x();instance.a();instance.b();instance.c(100);System.out.println(instance.f());}}在以上这段程序中：抽象类有：SuperAbstract和（1）(写出类名)非抽象类有：（2）(写出类名)接口有：（3）(写出接口名)AsSuper中的x()方法是（4）方法，所以在InheritAbstract中必须对它进行（5）9.publicclassSum{publicstaticvoidmain(String[]args){intj=10;System.out.println(jis:+j);calculate(j)