Java实验四深入面向对象

实验四深入面向对象

一、实验目的与要求

1、深刻理解面向对象的三大特征；

2、熟练掌握关键super、final的含义及用法；

3、理解什么是抽象类、抽象方法，以及两者间的关系；

4、深刻理解接口的概念、作用，以及与抽象类的差别；

5、类型的转换（向上和向下转换），运算符 instanceof的使用；

6、深刻理解、掌握动态多态性（难点重点）；

7、初步了解对象间进行消息传递的方式（两种一是乙类对象作为甲类的成员，二是对象作为方法的参数，本质是一样的）；

8、逐步掌握异常的分类、处理方法。

二、实验原理

1、面向对象的三大特征

面向对象的3大特征是封装、继承、多态。

封装：在定义一个类时都需要认真思考，类是现实世界中事物的属性和对这些属性进行操作的方法的集合体。因此一个类应该包括数据成员和函数成员，仅仅只含一种成员的类很少（除非特别需要），一般一个属性对应一对set、get，但并非set、get方法一定会成对出现。如何去进行类的封装呢？可以从操作反推属性的确定，即要完成哪些操作，这些操作的进行需要什么数据、得到怎样的结果。

继承：子类继承了父类非私有的成员，（实际上子类继承了父类的所有成员，只是私有的成员在子类中被隐藏了，通过方法还是可以访问到的）。可定义成员的访问权限时，不要把问题复杂化，即在实际应用中大多仅使用公共和私有权限。子类重写父类的方法时，不能缩小该方法的访问权限，（如果是缩小的、则子类的该方法就没有意义了，因为访问不到嘛）。

多态性：包含静态多态和动态多态，一般是指动态多态性。静态多态通过函数的重载实现，较为简单。困难的是动态多态，通过父子类、接口来实现。一般是父类的引用或者接口的引用指向子类的对象的形式。出现在赋值、做参数、方法的调用等位置。务必深刻理解。

三、实验内容、过程、结果（带*的本次不做，下次一起）

1、定义父类Person，派生出Teacher、Student。请选取合适的成员变量、方法。（考虑使用super、final、static关键字）

package test04;
public class Test {public static void main(String[] args){Student s = new Student();s.eat();s.sleep();System.out.println("---------");Teacher t = new Teacher();t.eat();t.sleep();t.teach();}
}
class Person{String name;void eat(){System.out.println("吃饭");}void sleep(){System.out.println("睡觉");}
}
class Student extends Person{int sid; //学号
}
class Teacher extends Person{int tid; //工号void teach(){System.out.println("老师教课");}
}

2、定义抽象类Shape（含求面积的抽象方法，常量PI），派生出圆、三角形（或者长方形、正方形、梯形）；由圆派生出圆锥体求体积。

package test04;
class Shape {public double pi;public double  GetCircle (double pi) {double s=3.14*3.14*pi;return s;}public static void main(String [] args) {Circle a=new Circle(3);Tangle b=new Tangle(3);System.out.println(a.GetCircle(3));System.out.println(b.GetTangle(3));}public double  GetTangle (double pi) {double s=pi*pi;return s;}public Shape(double pi) {super();this.pi = pi;}
}
class Circle extends Shape
{public Circle(double pi) {super(pi);}
}
class Tangle extends Shape
{public Tangle(double pi) {super(pi);}
}

*3、什么是适配器？定义一个接口包含求面积、体积的抽象方法，由此定义适配器，通过重写实现求圆、三角形的面积、圆锥体的体积。

适配器就是继承接口的类做父类派生出的子类能够重写父类的方法

package test04;
import java.util.Scanner;
interface Area {abstract double mianji(double x) ;abstract double mianji(double y,double z) ;abstract double  tiji(double r,double h)  ;public static void main (String [] args) {Scanner a=new Scanner (System.in);double x=a.nextDouble();Scanner b=new Scanner (System.in);double y=b.nextDouble();Scanner c=new Scanner (System.in);double z=c.nextDouble();Scanner d=new Scanner (System.in);double r=d.nextDouble();Scanner e=new Scanner (System.in);double h=e.nextDouble();area1 area2= new area1();System.out.println(area2.mianji(x));System.out.println(area2.mianji(y,z));System.out.println(area2.mianji(r,h));}
}
class area1 implements Area{public double mianji( double x) {double s1=3.14*x*x;return s1;}public double mianji( double y,double z) {double s2=0.5*z*y;return s2;}public double tiji(double r,double h) {double s3=1/3*3.14*r*r*h;return s3;}
}

4、根据Person类的属性、方法、Teacher派生类的属性方法，实现多态性(重点考查哪些能被访问、那些不能访问，及其规则)；

package test04;
class Person {public String name;public String work;public int leg;public String getName() {return name;}public void setName(String name) {this.name = name;}public String getWork() {return work;}public void setWork(String work) {this.work = work;}public Person(String name, String work) {this.name = name;this.work = work;}
}
class Teacher extends Person {public Teacher(String name, String work, String edu) {super(name, work);}public String edu;public void setWork(String teacher) {this.work = teacher;}public String getEdu() {return edu;}public void setEdu(String edu) {this.edu = edu;}
}
class Student extends Teacher {public Student(String name, String work,String edu) {super(name, work, edu);}public static void main(String[] args) {Person p = new Teacher("candice", "teacher", "graduate");System.out.println(p.getWork());System.out.println(p.getName());}
}

*5、使用Shape类、接口的数组，求圆、三角形的面积，实现多态性；

package test04;
public class text{public static void main( String [] args){try {class Shape {public double pi;public double  GetCircle (double pi) {double s=3.14*3.14*pi;return s;}public double  GetTangle (double pi) {double s=pi*pi;return s;}public Shape(double pi) {super();this.pi = pi;}}class Circle extends Shape{public Circle(double pi) {super(pi);}}class Tangle extends Shape{public Tangle(double pi) {super(pi);}public void main(String [] args ) {Circle a=new Circle(3);Tangle b=new Tangle(3);System.out.println(a.GetCircle(3));System.out.println(b.GetTangle(3));}}}catch(Exception e){e.printStackTrace();//打印错误//System.out.println("系统出错");}finally {System.out.println("最后");}}
}

*6、通过一个数组的值和下标、使用几种方式验证异常处理。

package test04;
public class testFinally {public static void main(String args[ ]) {  int a,b=0;for(int i=0;i<=3;i++){System.out.println("Test No: "+(i+1));try{  switch(i){case 0:   a=3/b;	break;case 1:   int  c[ ]=new int[10];c[10]=0;break;case 2:   char ch="ABC".charAt(99);break;case 3:   return;}}catch(ArithmeticException  e) {System.out.println("零作除数！");}catch(ArrayIndexOutOfBoundsException  e) {System.out.println("数组下标越界！");}catch(IndexOutOfBoundsException  e) {System.out.println("下标越界！");}finally{ System.out.println("在finally块中！");  }}}
}

7、实际应用（继承、重载）。

定义Employee（员工）类，由员工类派生出SaleMan（销售员）类和Manager（经理）类。要求：

(1)在员工类中包含有编号(num)、姓名(name)、工资(basicSalary)和奖金(prize)。在销售员类中还包含销售提成比例(deductRate)和个人销售额(personAmout)，在经理类中还包含经理提成比例(totalDeductRate)和总销售额(totalAmount)。

(2)各类人员的实发工资公式如下：

员工实发工资=基本工资+奖金

销售员 =基本工资+奖金+个人销售额*销售提成比例

经理 =基本工资+奖金+总销售额*经理提成比例

(3)每个类都有构造函数、输出基本信息的show方法、输出工资的showSalary的方法。

package test04;
public class Employee {public int num;public String name;public int salary;public int prize;public int showSalary(int salary,int prize) {int s;s=salary+prize;return s;}public static void main (String []args) {SaleMan n= new SaleMan(1,"Candice",5000,500,0.5,800);Manager m= new Manager(2,"Lucy",9000,1000,0.5,800);System.out.println("编号"+n.getNum() );System.out.println("姓名"+n.getName() );System.out.println("基本工资"+n.getPrize());System.out.println("个人销售额"+n.getPersonamout());System.out.println("销售提成比例"+n.getRate() );System.out.println("实际工资"+n.showSalary(5000, 500, 0.5, 800) );System.out.println("编号"+m.getNum() );System.out.println("姓名"+m.getName() );System.out.println("基本工资"+m.getPrize());System.out.println("个人销售额"+m.getTotalamount());System.out.println("销售提成比例"+m.getTotalrate());System.out.println("实际工资"+m.showSalary(9000, 1000, 0.5, 800) );}public int getNum() {return num;}public void setNum(int num) {this.num = num;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getSalary() {return salary;}public void setSalary(int salary) {this.salary = salary;}public int getPrize() {return prize;}public void setPrize(int prize) {this.prize = prize;}public Employee(int num, String name, int salary, int prize) {super();this.num = num;this.name = name;this.salary = salary;this.prize = prize;}
}
class SaleMan extends Employee{public SaleMan(int num, String name, int salary, int prize) {super(num,name,salary,prize);}public double rate;public int personamout;public double getRate() {return rate;}public void setRate(double rate) {this.rate = rate;}public int getPersonamout() {return personamout;}public void setPersonamout(int personamout) {this.personamout = personamout;}public SaleMan(int num, String name, int salary, int prize, double rate, int personamout) {super(num, name, salary, prize);this.rate = rate;this.personamout = personamout;}public double showSalary(int salary ,int prize ,double rate,int personamout) {double a;a= salary+ prize + rate*personamout;return a;}
}
class Manager extends Employee{public Manager(int num,String name,int salary, int prize) {super(num,name,salary,prize);}public double totalrate;public int totalamount;public double showSalary(int salary ,int prize ,double totalrate, int totalamount ) {double b;b=salary + prize + totalrate + totalamount;return b;}public double getTotalrate() {return totalrate;}public void setTotalrate(double totalrate) {this.totalrate = totalrate;}public int getTotalamount() {return totalamount;}public void setTotalamount(int totalamount) {this.totalamount = totalamount;}public Manager(int num, String name, int salary, int prize, double totalrate, int totalamount) {super(num, name, salary, prize);this.totalrate = totalrate;this.totalamount = totalamount;}
}