如何迭代不同对象的arraylist

Question

在ArrayList我有两个不同的对象, Student和Employee.我想逐个遍历它们.我能够遍历列表并使用Employee对象而不是Student对象.

我有以下代码:

package javaCollections;

import java.util.ArrayList;
import java.util.Iterator;

class Employee {

    @Override
    public String toString() {
        return "employee [name=" + name + ", age=" + age + "]";
    }

    public String name;
    public int age;

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    Employee(String name, int age) {
        this.age = age;
        this.name = name;
    }

}

class Student {

    @Override
    public String toString() {
        return "student [stud_name=" + stud_name + ", rollNumber=" + rollNumber
                + "]";
    }

    String stud_name;
    int rollNumber;

    public Student(String stud_name, int rollNumber) {
        super();
        this.stud_name = stud_name;
        this.rollNumber = rollNumber;
    }

    public String getStud_name() {
        return stud_name;
    }

    public void setStud_name(String stud_name) {
        this.stud_name = stud_name;
    }

    public int getRollNumber() {
        return rollNumber;
    }

    public void setRollNumber(int rollNumber) {
        this.rollNumber = rollNumber;
    }
}

public class Arraylist {

    ArrayList<Object> emparray;

    public void addemp() {
        Employee emp = new Employee("abc", 12);
        emparray = new ArrayList<Object>();
        emparray.add(emp);
        Employee emp1 = new Employee("def", 12);
        emparray.add(emp1);

        Student std = new Student("efg", 123);
        Student std1 = new Student("xyz", 123);
        emparray.add(std);
        emparray.add(std1);

    }

    public void iterateemp() {
        /*
         * Iterator<Object> itr=emparray.iterator();
         * 
         * while(itr.hasNext()) { System.out.println(itr.next()); }
         */

        for (Object e : emparray) {
            System.out.println(((Employee) e).getAge());
            System.out.println(((Employee) e).getName());
        }
    }

    public static void main(String[] args) {
        Arraylist al = new arraylist();
        al.addemp();
        al.iterateemp();
    }

}

有人可以帮我这个吗？

Answer 1

您需要做的是检查对象的实例.

for (Object e : emparray) {
        if(e instanceof employee) {
            System.out.println(((employee) e).getAge());
            System.out.println(((employee) e).getName());
        } else if(e instanceof student) {
            // do something else
        }
    }
}

IMO这是一个糟糕的设计.