具有不同类型对象的 ArrayList

Question

public static void main (String[] args)
{
  SalariedEmployee se = new SalariedEmployee();
  HourlyEmployee he = new HourlyEmployee();
  se.setName("Simos");
  se.setAfm("111440000");
  se.setSalary(4500);
  he.setName("Chatzis");
  he.setAfm("011155555");
  he.setHoursWorked(200);
  he.setHourlyPayment(25);
  ArrayList list = new ArrayList();
  list.add(se);
  list.add(he);
}

所以我有两个不同类型的对象，我想将它们添加到列表中。我怎样才能使它在编译器方面是安全的。由于对象是从不同的类创建的，所以在制作列表时我不能使用泛型。或者我可以在创建列表后更改列表的类型。我的意思是我可以拥有这个

ArrayList<SalariedEmployee> list = new ArrayList<SalariedEmployee>();

添加SalriedEmployee的“se”对象，然后将泛型更改为HourlyEmployee，然后添加HourlyEmployee的“he”对象？

Answer 1

看起来你可以创建通用接口Employee 并让两个类都实现它。这样你就可以使用泛型了：

List<Employee> list = new ArrayList<Employee>();

Answer 2

创建界面：

Employee.java

public interface Employee {
    public void setName(String name);
    public String getName();

    public void setAfm(String afm);
    public String getAfm();

}

然后创建实现它的两个类，添加它们的独特方法：

HourlyEmployee.java

public class HourlyEmployee implements Employee {

    private String name;
    private String afm;
    private int hoursWorked;
    private int hourlyPayment;

    @Override
    public void setName(String name) {
        this.name = name;

    }

    @Override
    public String getName() {
        return this.name;
    }

    @Override
    public void setAfm(String afm) {
        this.afm = afm;
    }

    @Override
    public String getAfm() {
        return this.afm;
    }

    public int getHoursWorked() {
        return this.hoursWorked;
    }

    public void setHoursWorked(int hoursWorked) {
        this.hoursWorked = hoursWorked;
    }

    public int getHourlyPayment() {
        return this.hourlyPayment;
    }

    public void setHourlyPayment(int hourlyPayment) {
        this.hourlyPayment = hourlyPayment;
    }
}

SaliedEmployee.java

public class SalariedEmployee implements Employee {

    private String name;
    private String afm;
    private int salary;

    @Override
    public void setName(String name) {
        this.name = name;

    }

    @Override
    public String getName() {
        return this.name;
    }

    @Override
    public void setAfm(String afm) {
        this.afm = afm;

    }

    @Override
    public String getAfm() {
        return this.afm;
    }

    public int getSalary() {
        return this.salary;
    }

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

}

然后进行测试：

import java.util.ArrayList;

public class TestMain {

    public static void main(String[] args){
         SalariedEmployee se = new SalariedEmployee();
          HourlyEmployee he = new HourlyEmployee();
          se.setName("Simos");
          se.setAfm("111440000");
          se.setSalary(4500);
          he.setName("Chatzis");
          he.setAfm("011155555");
          he.setHoursWorked(200);
          he.setHourlyPayment(25);
          ArrayList<Employee> list = new ArrayList<Employee>();
          list.add(se);
          list.add(he);

    }
}

Answer 3

创建一个 Employee 类，这两个可以继承并在 ArrayList 中使用它

public abstract class Employee 
{
    public string setName(string name) { ... }
    public string setAfm(string afm) { ... }
    public int setSalary(float afm) { ... }
}

public class HourlyEmployee extends Employee
{
}

public class SalariedEmployee extends Employee
{
}

ArrayList<Employee> employees;

这也意味着您不必为每个员工类重写 setter 方法

Answer 4

你为什么不创建一个超类“员工”并让两个对象都成为员工的孩子：

class Employee { }
class SalariedEmployee extends Employee { }
class HourlyEmployee extends Employee { }

Employee salariedEmp = new SalariedEmployee();
Employee hourlyEmp = new HourlyEmployee();

然后创建一个Employee类型的数组列表：

ArrayList<Employee> list = new <Employee>ArrayList();

Answer 5

下面的初始化添加到列表中。

> List<Object> list = new <Object>ArrayList();

要稍后从列表中读取，您可以使用 instanceof 并强制转换为您在代码中拥有的已知类型。