Question

我在java中创建了三个类：

CollegeCourse

package CollegeCourse;
import javax.swing.JOptionPane;
public class CollegeCourse {

protected String Dept;
protected int CourseNum;
protected int Cred;
protected int fee;
protected int Charge = 120;
protected int labfee;

public void inputDepartment(){
    Dept = JOptionPane.showInputDialog(null, "Enter Department");
}

public void inputCourseNumber(){
    String CourseNumString = new String(" ");
    CourseNumString = JOptionPane.showInputDialog(null, "Enter Course Number");
    CourseNum = Integer.parseInt(CourseNumString);
}

public void inputCredits(){
    String CredString = new String(" ");
    CredString = JOptionPane.showInputDialog(null, "Enter Credits");
    Cred = Integer.parseInt(CredString);
}

 public void displayNonLabCourse(){
    fee = Cred * Charge;
    JOptionPane.showMessageDialog(null, Dept + CourseNum + 
            "\nNon-lab Course" + "\n" + Cred +" Credits" + "\nTotal fee is $" + fee);
 }

}

LabCourse

package CollegeCourse;
import javax.swing.JOptionPane;
public class LabCourse extends CollegeCourse {

 public void displayLabCourse(){
    labfee = fee + 50;
    JOptionPane.showMessageDialog(null, Dept + CourseNum + 
            "\nLab Course" + "\n" + Cred +" Credits" + "\nTotal fee is $" + fee);
 }
 }

UseCourse

package CollegeCourse;
public class UseCourse{
public static void main(String[] args) {
    CollegeCourse college = new CollegeCourse();
    college.inputDepartment();
    college.inputCourseNumber();
    college.inputCredits();
    college.displayNonLabCourse();
    }
}

当用户进入某个部门如“BIO”时，如何让UseCourse类显示LabCourse显示方法？

创建一个名为CollegeCourse的类，其中包含保存部门的数据字段（例如，ENG），课程编号（例如，101），学分（例如3），和课程费用（例如，360美元）。所有字段都是必需的参数到建设者，费用除外，每小时120美元计算。包括显示课程数据的display（）方法。创建一个名为LabCourse的子类增加50美元的课程费用。覆盖父类display（）方法以指示课程是一个显示所有数据的实验课程。写一个名为UseCourse的应用程序提示用户提供信息。如果用户在以下任何部门中输入课程，创建LabCourse：BIO，CHM，CIS或PHY。如果用户进入任何其他部门，请创建不包括实验室费用的CollegeCourse。然后显示课程数据。保存文件作为CollegeCourse.java，LabCourse.java和UseCourse.java。

Answer 1

这与您的原始实现完全不同。但我相信它能满足您的需求。可能有更好的方法来实现它，但我只是根据你给我的信息来实现。希望你能理解这一切...

UseCourse：

import javax.swing.JOptionPane;

public class UseCourse
{   
    public UseCourse()
    {
        CollegeCourse college;
        // Collect all the necessary data first to determine whether it is a lab course or not.
        String dept = JOptionPane.showInputDialog(null, "Enter Department");

        String courseNumString = JOptionPane.showInputDialog(null, "Enter Course Number");
        int courseNum = Integer.parseInt(courseNumString);

        String credString = JOptionPane.showInputDialog(null, "Enter Credits");
        int cred = Integer.parseInt(credString);

        // Now that we have the info we can ask the question.
        if (dept.equals("BIO") | dept.equals("CHM") | dept.equals("CIS") | dept.equals("PHY"))
        {college = new LabCourse(dept, courseNum, cred);}

        else {college = new LabCourse(dept, courseNum, cred);}
        college.display();
    }

    public static void main(String[] args) 
    {new UseCourse();}
}

CollegeCourse：

import javax.swing.JOptionPane;
public class CollegeCourse {

protected String dept;
protected int courseNum;
protected int cred;
protected int fee;
protected int Charge = 120;
protected int labfee;

public CollegeCourse(String dept, int courseNum, int cred)
{
    this.dept = dept;
    this.courseNum = courseNum;
    this.cred = cred;
    fee = cred * Charge;
}

public void display(){

    JOptionPane.showMessageDialog(null, dept + courseNum + 
            "\nNon-lab Course" + "\n" + cred +" Credits" + "\nTotal fee is $" + fee);
 }
}

LabCourse：

import javax.swing.JOptionPane;
public class LabCourse extends CollegeCourse 
{
    public LabCourse(String dept, int courseNum, int cred)
    {super(dept, courseNum, cred);}

    public void display()
    {
        fee += 50;
        JOptionPane.showMessageDialog(null, dept + courseNum + 
                "\nLab Course" + "\n" + cred +" Credits" + "\nTotal fee is $" + fee);
    }  
}

Answer 2

如果你想使用继承来做这个，那么你应该使用相同的方法名称，例如＆＃34; displayCourse＆＃34;在CollegeCourse和LabCourse课程。然后根据用户的输入：

CollegeCourse c = null;
if (userSelectedCollegeCourse) {
c = new CollegeCourse(param1, ...);
}else{
c = new LabCourse(param1, ...);
}

c.displayCourse();

在java中使用继承和对话框

2 个答案: