初识java继承

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实验练习 Employee层次结构

程序模板是一个完整的、可实际运行的JAVA程序，其中关键的1行或者多行代码已经替换为注释。请先阅读问题描述，分析示例输出；然后研究模板的代码。参考问题解答提示，用JAVA代码替换注释。编译并执行程序，并将输出结果与提供的示例输出进行比较。然后回答后续问题。

1、实验目的

l 建立一个类层次结构

l 创建正确调用超类构造函数的子类构造函数

l 使用类层次结构中的类

l 将某个类添加到现有的类层次结构中

2、问题描述

创建类图中的各个类。Employee类应有姓、名和社会保险号。除以上这些外，SalariedEmployee类还应有周薪；HourlyEmployee类还应有每小时工资和工作时数；

CommissionEmployee还应有佣金率和销售总额。每个类都应有合适的构造函数、设置方法和读取方法。编写一个程序，实例化这些类的对象，并输出与每个对象相关的信息（包括所继承的信息。）

3、示例输出

4、程序模板

// Lab 1: Employee.java

// Employee superclass.

public class Employee {

/* Declare instance variables for the first name,

last name and social security number. */

// constructor

/* Declare a constructor with three parameters that are used to

initialize the first name, last name and social security number. */

// set methods

/* Create set methods for every instance variable. */

// get methods

/* Create get methods for every instance variable. */

// return String representation of Employee object

/* Create a toString method that returns a String containing the first name

and last name separated by a space. Then, append a newline and the social security number. */

} // end class Employee

// Lab 1: SalariedEmployee.java

// SalariedEmployee class derived from Employee.

/* Write a class header in which class SalariedEmployee

inherits from class Employee */

/* Declare an instance variable for the weekly salary. */

// constructor

/* Declare a constructor that initializes all the data for a SalariedEmployee,

including the data originally defined in class Employee. */

// set methods

/* Create a set method for the instance variable. */

// get methods

/* Create a get method for the instance variable. */

// return String representation of SalariedEmployee object

/* Create a toString method that outputs the complete information

for a SalariedEmployeex. */

} // end class SalariedEmployee

// Lab 1: CommissionEmployee.java

// CommissionEmployee class derived from Employee.

/* Write a class header in which class CommissionEmployee

inherits from class Employee */

/* Declare instance variables for gross sales and commission rate. */

// constructor

/* Declare a constructor that initializes all the data for a CommissionEmployee,

including the data originally defined in class Employee. */

// set methods

/* Create set methods for every instance variable. */

// get methods

/* Create get methods for every instance variable. */

// return String representation of CommissionEmployee object

/* Create a toString method that outputs the complete information

for a CommissionEmployee. */

} // end class CommissionEmployee

// Lab 1: HourlyEmployee.java

// HourlyEmployee class derived from Employee.

/* Write a class header in which class HourlyEmployee

inherits from class Employee */

/* Declare instance variables for wages and hours worked. */

// constructor

/* Declare a constructor that initializes all the data for a HourlyEmployee,

including the data originally defined in class Employee. */

// set methods

/* Create set methods for every instance variable. */

// get methods

/* Create get methods for every instance variable. */

// return String representation of HourlyEmployee object

/* Create a toString method that outputs the complete information

for a HourlyEmployee. */

} // end class HourlyEmployee

// Lab 1: EmployeeTest.java

// Employee hierarchy test program.

import java.text.DecimalFormat;

import javax.swing.JOptionPane;

public class EmployeeTest {

public static void main( String[] args )

{

DecimalFormat twoDigits = new DecimalFormat( "0.00" );

// Create employees

/* Create SalariedEmployee John Smith with social security number

111-11-1111 and weekly salary $800.00. */

/* Create SalariedEmployee Sue Jones with social security number

222-22-2222 with gross sales of $10000 and a commission rate of .06. */

/* Create SalariedEmployee Karen Price with social security number

444-44-4444 an hourly salary of $16.75 and 40 hours worked. */

// output each employee

/* Create a String called output and assign it the String representation

of the three employee objects separated by newlines. */

JOptionPane.showMessageDialog( null, output ); // display output

System.exit( 0 );

} // end main

} // end class EmployeeTest

5、问题解答提示

（1）每个扩展Employee的类的构造函数都应调用Employee构造函数，并将姓、名和社会保险号传递给它。

（2）每个扩展Employee的类的toString方法都应调用Employee类的toString方法，以获取姓、名和社会保险号的String表示，然后在返回的String中添加额外的信息。

（3）练习中有任何问题请及时询问老师。

6、强化练习

（1）改进实验练习1的类层次结构，使其包含BasePlusCommissionEmployee类。BasePlusCommissionEmployee类与CommissionEmployee类具有相同的特征，但是还包括每星期的基本工资。该类的构造函数应调用CommissionEmployee类的构造函数；而该类的toString方法应调用CommissionEmployee类的toString方法。在创建BasePlusCommissionEmployee类后，改进实验1的程序，以实例化这个新类的一个对象，并输出该对象的信息（包括它所继承的信息）。输出结果应如下所示。

下面是我自己写的代码，基本能够实现实验一的内容， Employee1.0

Employee类是下面所有******Employee类的父类

package com.whj.exam;public class Employee {    private String thefirstname;    private String thelastname;    private String  socialnumber;    public Employee(String thefirstname, String thelastname, String socialnumber)     {    //super();继承Employee的父类的构造方法，Employee的父类是object；    this.thefirstname = thefirstname;    this.thelastname = thelastname;    this.socialnumber = socialnumber;    }public String getThefirstname() {return thefirstname;}public void setThefirstname(String thefirstname) {this.thefirstname = thefirstname;}public String getThelastname() {return thelastname;}public void setThelastname(String thelastname) {this.thelastname = thelastname;}public String getSocialnumber() {return socialnumber;}public void setSocialnumber(String socialnumber) {this.socialnumber = socialnumber;}@Overridepublic String toString() {return getClass().getName()+":"+getThefirstname()+getThelastname()+"\n"+"social  security number:"+getSocialnumber();}}

测试类，包含主方法

package com.whj.exam;import java.text.DecimalFormat;import javax.swing.JOptionPane;public class Test {public static void main(String[] args) {DecimalFormat twoDigits = new DecimalFormat( "0.00" );      Employee employee[]=new Employee[3];      employee[0]=new SalariedEmployee("John", "Smith", "111-11-1111","$800.00");              employee[1]=new CommissionEmployee("Sue", "Jones", "222-22-2222","$10000",".06");              employee[2]=new HourlyEmployee("Karen", "Price","444-44-4444","$16.75","40");      String output;          output=employee[0].toString()+"\n"+employee[1].toString()+"\n"+employee[2].toString();      JOptionPane.showMessageDialog( null, output );       System.exit( 0 );}}

SalariedEmployee类，是Employee的继承子类，其中多了每周的薪金。

package com.whj.exam;public class SalariedEmployee extends Employee {private  String salary;public SalariedEmployee(String thefirstname, String thelastname,String socialnumber, String salary) {super(thefirstname, thelastname, socialnumber);this.salary = salary;}public String getSalary() {return salary;}public void setSalary(String salary) {this.salary = salary;}@Overridepublic String toString(){return super.toString()+"\n"+"weekly salary:"+getSalary()+"\n";}}

CommissionEmployee类，是Employee的子类，其中多了佣金率和销售总额。

package com.whj.exam;public class CommissionEmployee extends Employee{     private String grosssales;     private String commissionrate;public CommissionEmployee(String thefirstname, String thelastname,String socialnumber, String grosssales, String commissionrate) {super(thefirstname, thelastname, socialnumber);this.grosssales = grosssales;this.commissionrate = commissionrate;}public String getGrosssales() {return grosssales;}public void setGrosssales(String grosssales) {this.grosssales = grosssales;}public String getCommissionrate() {return commissionrate;}public void setCommissionrate(String commissionrate) {this.commissionrate = commissionrate;}@Overridepublic String toString() {return super.toString()+"\n"+"gross sales:"+getGrosssales()+"\n"+"a commission rate:"+getCommissionrate()+"\n";}}

HourlyEmployee类，是Employee的子类，其中添加了每小时工资和工作时数。

package com.whj.exam;public class HourlyEmployee extends Employee{   private String hourlysalary;   private String workhour;public String getHourlysalary() {return hourlysalary;}public void setHourlysalary(String hourlysalary) {this.hourlysalary = hourlysalary;}public String getWorkhour() {return workhour;}public void setWorkhour(String workhour) {this.workhour = workhour;}public HourlyEmployee(String thefirstname, String thelastname,String socialnumber, String hourlysalary, String workhour) {super(thefirstname, thelastname, socialnumber);this.hourlysalary = hourlysalary;this.workhour = workhour;}@Overridepublic String toString() {return  super.toString()+"\n"+"hourly salary:"+getHourlysalary()+"\n"+"hours worked:"+getWorkhour()+"\n";}   }

通过老师给的实验对java中继承的初步运用，其中的一些细节还是有点把握不清，还有实验一扩展练习没做。（employee 2.0）

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