如何设置一个对象的变量的值在一个ArrayList

本文介绍了如何设置一个对象的变量的值在一个ArrayList的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我的工作分配中，我有：

创建具有以下属性/变量的Employee类：名称年龄部门

创建一个名为Department类其中将包含员工的列表。

一个。 Department类将有将返回其员工按年龄排序的方法。

乙。系数值只能是下列之一：

• 会计学
• 市场营销
• 人力资源
• 信息系统

我有困难的时候试图找出如何完成2B。以下是我迄今为止：

进口的java.util。*;公共类Employee {字符串名称;INT年龄;串部门;员工（字符串名称，诠释年龄，弦乐部）{    this.name =名称;    this.age =年龄;    this.department =部;}INT getAge（）{    返回年龄;}}类系{公共静态无效的主要（字串[] args）{    清单＆LT;员工＆GT; empList =新的ArrayList＆LT;员工＆GT;（）;    Collections.sort（empList，新的比较＆LT;员工＆GT;（）{        公众诠释比较（员工E1，E2员工）{            返回新的整数（e1.getAge（））的compareTo（e2.getAge（））;        }    }）;    }}

解决方案

您可以使用，这将限制你只能使用指定的值相同的目的枚举。声明你的处枚举如下：

公共枚举系{    会计，Marketting，Human_Resources，Information_Systems}

现在

您员工类可以是

公共类Employee {    字符串名称;    INT年龄;    系部;    员工（字符串名称，诠释年龄，系部）{        this.name =名称;        this.age =年龄;        this.department =部;    }    INT getAge（）{        返回年龄;    }}

和同时创造员工，你可以使用

员工员工=新员工（普拉萨德，47，Department.Information_Systems）;

修改按阿德里安深当然，因为它是一个伟大的建议的建议。

• 的枚举是这就是为什么其良好的大写字母根据Java约定声明常量。
• 但是，我们不希望枚举的资本重新presentation待观察，所以我们可以创建枚举构造，并通过读取信息给它。

• 我们西港岛线修改枚举包括的toString（）方法和构造，它接受一个字符串参数。

  公共枚举系{   会计（会计），MARKETTING（Marketting），HUMAN_RESOURCES（        人力资源），INFORMATION_SYSTEMS（信息系统）;   私人字符串DEPTNAME;    部（字符串DEPTNAME）{       this.deptName = DEPTNAME;    }   @覆盖   公共字符串的toString（）{    返回this.deptName;   }}

所以，当我们正在创建一个员工对象，如下所示，使用它

员工员工=新员工（普拉萨德Kharkar，47，Department.INFORMATION_SYSTEMS）;的System.out.println（employee.getDepartment（））;

我们会得到一个可读的字符串重新presentation为信息系统因为它是由返回的toString（）方法，它是通过的System.out.println（）语句。阅读关于枚举

I am working on an assignment in which I have to:

Create an Employee class with the following attributes/variables: name age department

Create a class called Department which will contain a list of employees.

a. Department class will have a method which will return its employees ordered by age.

b. Value of Department can be only one of the following:

• "Accounting"
• "Marketing"
• "Human Resources"
• "Information Systems"

I am having the hardest time trying to figure out how to complete 2b. Here is what I have so far:

import java.util.*; public class Employee { String name; int age; String department; Employee (String name, int age, String department) { this.name = name; this.age = age; this.department = department; } int getAge() { return age; } } class Department { public static void main(String[] args) { List<Employee>empList = new ArrayList<Employee>(); Collections.sort (empList, new Comparator<Employee>() { public int compare (Employee e1, Employee e2) { return new Integer (e1.getAge())pareTo(e2.getAge()); } }); } }

解决方案

You can use enumerations for the same purpose which will restrict you to use only specified values. Declare your Department enum as follows

public enum Department { Accounting, Marketting, Human_Resources, Information_Systems }

You Employee class can now be

public class Employee { String name; int age; Department department; Employee(String name, int age, Department department) { this.name = name; this.age = age; this.department = department; } int getAge() { return age; } }

and while creating employee, you can use

Employee employee = new Employee("Prasad", 47, Department.Information_Systems);

EDIT as suggested by Adrian Shum and of course because it is a great suggestion.

• The enums are constants thats why its good to be declared in capital letters according to java conventions.
• But we don't want the capital representation of the enums to be seen so we can create enum constructors and pass readable info to it.

• We wil modify enum to include toString() method and constructor which takes a string argument.

  public enum Department { ACCOUNTING("Accounting"), MARKETTING("Marketting"), HUMAN_RESOURCES( "Human Resources"), INFORMATION_SYSTEMS("Information Systems"); private String deptName; Department(String deptName) { this.deptName = deptName; } @Override public String toString() { return this.deptName; } }

So when we are creating an Employee object as follows and using it,

Employee employee = new Employee("Prasad Kharkar", 47, Department.INFORMATION_SYSTEMS); System.out.println(employee.getDepartment());

We will get a readable string representation as Information Systems as it is returned by toString() method which is called implicitly by System.out.println() statement. Read the good tutorial about Enumerations