Question

我想用Java建模以下类：

enter image description here

所以我带来了以下代码：

class Person
{
    private String name;
    private ing age;
    public Person(String name, int age){
        this.name=name;
        this.age=age;
    }
    //set and get methods
}

class Employee
{
    private String nameEmp;
    private double salary;
    public Employee(String nameEmp, double salary){
        this.nameEmp=nameEmp;
        this.salary=salary;
    }
    public double calcSalary(){}   //should this be an abstract method?
}

class Teacher extends Person implements Employee
{
    private String nameTeacher;
    private int ageTeacher;
    private String title;   //professor or lecturer
    public Teacher(String nameTeacher,int ageTeacher, String title){
        super(nameTeacher,ageTeacher);
        this.title=title;
    }
    public double calcSalary(){
        if (title.equals("Professor")) salary=salary*0,30;
        else if (title.equals("Lecturer")) salary=salary*0,10;
    }
}

我想使用接口对其进行建模，但我不太清楚如何做到这一点。 calcSalary也应该是Employee中的抽象方法？如何使用Java中的接口实现这一点？

由于

Answer 1

不，你不能这样做，你应该去老师是 - ＆gt;员工是 - ＆gt;人。你无法在界面中实现任何东西！接口只能包含应由类实现的方法。

Answer 2

你可以这样：

public interface Person{
    // Only abstract methods here
}

public interface Employee extends Person {
    // Only abstract methods here specific to Employee
}

public class Teacher implements Employee {
    //Implements the methods 
}

Answer 3

Java 8允许您在接口中放置默认实现。在此之前，接口不能包含实现。

Answer 4

从Person开始。那里有一个错字：

public class Person
{
    private String name;
    private int age;
    public Person(String name, int age){
        this.name=name;
        this.age=age;
    }
    // set and get methods, equals, hashCode, toString,
    // perhaps an id for database storage.
}

现在，有些Person是Employee个;其他人是学生，家长，未来学生等。如果Employee的任何方法都有实现，则它不能是接口。在任何情况下，nameEmp都是错误的，因为它会在Person中复制该名称。您可以为Employee创建一个混合到Teacher类中的接口，或者从Employee继承。

或者：

public interface Employee {
    // Currency values should use BigDecimal or BigInteger, not double.
    BigDecimal salary();
    // Taxpayer Identification Number (SSN) in the USA, or the equivalent outside.
    String taxNumber();
}

或：

public class Employee extends Person {

    private BigDecimal salary;
    private String taxNumber;
    public Employee(String name, int age, BigDecimal salary,
                    String taxNumber) {
        super(name, age);
        this.salary = salary;
        this.taxNumber = taxNumber;
        this.title = title;
    }
    // getters, setters, etc.
}

public class Teacher extends Employee {
    private Department department;
    private List<Course> courses = new ArrayList<>();
    // Constructors, getters, setters, etc.
}

如果他们需要一个完全不同的实现，你应该只有教师的薪水方法。您可能希望在Employee类中使用某种pay calaculator类（策略模式）。通过这种方式，您可以在适用的情况下处理应税扣除，保险，养老金计划和加班费。我不理解原始例子中的乘数。

Answer 5

public interface Person {
    String getName();
    void setName(String name);
    int getAge();
    void setAge(int age);
}

public class PersonImpl implements Person {
    private String name;
    private int age;
    @override public String getName() { return this.name; }
    @override public void setName(String name) { this.name = name; }
    @override public int getAge() { return this.age; }
    @override public void setAge(int age) { this.age = age; }
}

public interface Employee extends Person {
    double getSalary();
    void setSalary(double salary);
    double calcSalary();
}

public abstract class EmployeeImpl extends PersonImpl implements Employee {
    private double salary;
    @override public double getSalary() { return this.salary; }
    @override public void setSalary(double salary) { this.salary = salary; }
}

public class Teacher extends EmployeeImpl
    @override public double calcSalary() { 
        if (title.equals("Professor")) salary=salary*0,30;
        else if (title.equals("Lecturer")) salary=salary*0,10;
    }
}

Java中的多重继承问题

5 个答案: