在 main 方法中调用超类

Question

我刚刚学习了 superclasses 和 subclasses，作业很简单：有 2 个 classes 和一个测试 class调用并打印属性。以下是我所有 3 classes 的代码。我的问题是，为什么部门属性没有打印在我的主要文件中？其他一切都打印得很好，我只是无法打印最后一点。我认为这与超级有关......提前谢谢你！第二门计算机课程，我终于觉得我有点明白了，所以这是我参加的第一个 class 的进步！


public class Employee {

    private String firstName;
    private String lastName;
    private int employeeID;
    private double salary;

    public Employee () {

        firstName = null;
        lastName = null;
        employeeID = 0;
        salary = 0.00;
    }

    public String getFirstName() {
        return firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public int getEmployeeID() {
        return employeeID;
    }

    public double getSalary() {
        return salary;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public void setEmployeeID(int employeeID) {
        this.employeeID = employeeID;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public String employeeSummary () {
        String employeeSummary = "Employee's name is: " + getFirstName() + " " + getLastName() +
                    ". The employee's ID number is " + getEmployeeID() + 
                    ". The employee's salary is " + getSalary();
        System.out.println(employeeSummary);
        return employeeSummary;
    }

}


public class Manager extends Employee {

    private String departmentA;

    public Manager() {
        super();
        departmentA = null;
    }

    public String getDepartmentA() {
        return departmentA;
    }

    public void setDepartmentA(String departmentA) {
        this.departmentA = departmentA;
    }

    public void EmployeeSummary() {
        super.employeeSummary();
        System.out.println("The employee's department is " + departmentA);
    }
}


public class ManagerDerivation {

    public static void main(String[] args) {
        Manager person = new Manager();

        person.setFirstName("Ron");
        person.setLastName("Weasley");
        person.setEmployeeID(2345);
        person.setSalary(65000.00);
        person.setDepartmentA("Department of Magical Law Enforcement");
        person.employeeSummary();

    return;

    }

}

Answer 1

方法名称区分大小写。 EmployeeSummary() 不会覆盖 employeeSummary()，因为它使用了不同的名称。

为避免此类错误，请始终在重写的方法中包含 @Override annotation。如果包含该注释并在方法签名中出错，编译将失败。

另请注意，这两种方法的 return 类型不同（String 和 void）。覆盖的方法必须具有兼容的 return 类型。

Answer 2

存在一些拼写错误（employeeSummary 与 EmployeeSummary）并且 return 类型不匹配，在 Employee 中应该是

public void employeeSummary () {
    String employeeSummary = "Employee's name is: " + getFirstName() + " " + 
    getLastName() +
                ". The employee's ID number is " + getEmployeeID() + 
                ". The employee's salary is " + getSalary();
    System.out.println(employeeSummary);   
}

然后在管理器中

public void employeeSummary() {
    super.employeeSummary();
    System.out.println("The employee's department is " + departmentA);
}

在 main 方法中调用超类

Calling superclass in main method

java

polymorphism

subclass

superclass