期末复习题

}

public static void main(String[] args) {

Student s1=new Student(\,\男\,20,'A'); s1.print();

}

7．定义一个类Rectangle代表矩形，其中包括计算面积的方法。再定义一个它的子类Square代表正方形]，其中也包含计算面积的方法。编写一程序，测试新建子类对象的属性和方法？ class Rectangle{ float length; float width; Rectangle(float len,float wh){ length=len; width=wh; } float getArea(){ return length*width; } }

class Square extends Rectangle{ float length; Square(float len){ super(len,len); length=len; } float getArea(){ return super.getArea(); } }

public class TestRectangle{ public static void main(String[] args){ Square sq=new Square(5.2f); System.out.println(\ } } 8．定义一个Document类，包含成员属性name。从Document派生出Book子类，增加PageCount变量，编写一应用程序，测试定义的类？ class Document{ String name; Document(String str){ name=str; }

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void show(){ System.out.println(name); } }

class Book extends Document{ int PageCount; Book(String name,int n){ super(name); PageCount=n; } void show(){ System.out.print(\ super.show(); System.out.println(\ } }

public class TestDoc{ public static void main(String[] args){ Book book1=new Book(\ book1.show(); } }

9．编写一个Java应用程序，设计一个汽车类Vehicle，包含的属性有车轮个数wheels和车重weight。小车类Car是Vehicle的子类，其中包含的属性有载人数loader。卡车类Truck是Car类的子类，其中包含的属性有载重量payload。每个类都有构造方法和输出相关数据的方法。 class Vehicle { int wheels; float weight;

Vehicle（int wh,float we） ｛ wheels=wh; weight=we;

｝

int getWheels(){return wheels;} float getWeight(){return weight;} void show() {

System.out.println(“车轮：”+wheels); System.out.println(“车重：”+weight); } }

class Car extends Vehicle {

int loader;

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Car(int wheels,float weight,int loader) {super(wheels,weight); this.loader=loader;} }

public void show() {

System.out.println(“车型：小车”); super.show();

System.out.println(“载人：”+loader); }

class Truck extends Car {

float payload;

Truck(int wheels,float weight,int loader,float payload) {super(wheels,weight,loader); this.payload=payload;} }

public void show() {

System.out.println(“车型：卡车”); super.show();

System.out.println(“载重量：”+payload); }

public class VehicleClient {

public static void main(String[] args) {

Car car=new Car(4,1500,4); car.show();

Truck truck=new Truck(8,7000,3,25000); truck.show(); } }

10．一个关于等边三角形的类Trival如下，其中的属性包括三角形的bian，方法包括：默认构造方法、为bian指定初值的构造方法、获取三角形面积findArea()。试利用方法覆盖的知识，设计三棱柱体类TriCylinder。（其中findArea()为计算三棱柱体的表面积） class Trival { double bian; Trival() { bian=1.0; } Trival(double b)

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{ bian=b; }

double findArea() {

return (3/4)*bian*bian;

} }

答案：

public class TestOverrideMethods {

public static void main(String[] args) {

Cylinder myTriCylinder = new TriCylinder(5.0, 2.0);

System.out.println(\ System.out.println(\ System.out.println(\ myTriCylinder.findArea()); } }

class TriCylinder extends Trival {

private double length;

// Default constructor public Cylinder() {

super(); length = 1.0; }

public Cylinder(double r, double l) {

super(r); length = l; }

// Getter method for length public double getLength() {

return length;

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