java - 我如何区分这些对象(即 FirstLevelEmployee 和 SecondLevelEmployee)并且我想打印 SecondLevelEmployee 的详细信息？

Question

在下面的代码中，我创建了父类和子类对象。这些对象存储在数组列表中。我的问题是如何区分这些对象，并且我只想检索二级员工详细信息。

package com.javahonk.controller;

import java.util.ArrayList;
import java.util.ListIterator;

class FirstLevelEmployee {
    int id;
    String name;
    double salary;

    FirstLevelEmployee(int id, String name, double salary) {
        super();
        this.id = id;
        this.name = name;
        this.salary = salary;
    }
}

class SecondLevelEmployee extends FirstLevelEmployee {
    int experience;

    SecondLevelEmployee(int id, String name, double salary, int experience) {
        super(id, name, salary);
        this.experience = experience;
    }
}

public class EmployeeDemo {

    public static void main(String[] args) {
        ArrayList<FirstLevelEmployee> emps = new ArrayList<>();
        emps.add(new FirstLevelEmployee(1, "aaa", 20000.00));
        emps.add(new FirstLevelEmployee(2, "bbb", 10000.00));
        emps.add(new FirstLevelEmployee(3, "bbb", 30000.00));
        emps.add(new SecondLevelEmployee(4, "zzz", 12000, 2));
        emps.add(new SecondLevelEmployee(6, "yyy", 45000.00, 5));
    }
}

Answer 1

尝试这样做:

for(FirstLevelEmployee emp : emps){
     if(emp instanceof SecondLevelEmployee){
          System.out.println(((SecondLevelEmployee)emp).experience); 
     }
}

您将迭代该数组，并询问给定元素 emp 是否是 SecondLevelEmployee 的实例。如果为 true，您将通过将 emp 转换为 SecondLevelEmployee

来打印它