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/*例子：定义一个员工类Employees,使用一个变量restday来表示他哪一天休息*///-------------------------------version:0.1----------------------/*class Employees{ private int restday; //一周的哪一天休息 public int getRestday() { return restday; } public void setRestday(int restday) { this.restday = restday; }}public class EnumerateDemo{ public static void main(String[] args) { Employees e = new Employees(); //创建员工对象 e.setRestday(2); //设置休息时间 int restday = e.getRestday(); if(restday == 6 || restday == 7) { System.out.println("周末休息..."); } else { System.out.println("周一至周五休息..."); } }}上述代码的问题：1、数据类型不安全 （可以传入float等）2、数据范围不安全 （可以设置任何数字）3、数据表示的含义不明确 （3表示什么？）*///----------------------------version:0.2(对发现的问题进行改进)-----------------------------//定义一个星期几的常量类/*class Weekday{ public static final int Monday = 1; public static final int Tuesday = 2; public static final int Wednesday = 3; public static final int Thursday = 4; public static final int Friday = 5; public static final int Saturday = 6; public static final int Sunday = 7;}class Employees{ private int restday; //一周的哪一天休息 public int getRestday() { return restday; } public void setRestday(int restday) { this.restday = restday; }}public class EnumerateDemo{ public static void main(String[] args) { Employees e = new Employees(); //创建员工对象 e.setRestday(Weekday.Wednesday); //通过引用常量设置休息时间 int restday = e.getRestday(); //得到值 if(restday == 6 || restday == 7) { System.out.println("周末休息..."); } else { System.out.println("周一至周五休息..."); } }}解决的问题：1、数据表示的含义明确性已经提高，Monday = 1; 表示周一依然存在问题：1、数据类型还是不安全2、数据范围不安全 （还是可以设置任何数字）*///--------------------------------version:0.3--------------------------------//将原来的常量类改写：封装成对象的方式class Weekday{ private Weekday(){}; //预防创建对象，私有化构造函数 public static final Weekday Monday = new Weekday(); //因为int类型不安全，因此改写对象,Monday变量存储的是Weekday类型的对象 public static final Weekday Tuesday = new Weekday(); public static final Weekday Wednesday = new Weekday(); public static final Weekday Thursday = new Weekday(); public static final Weekday Friday = new Weekday(); public static final Weekday Saturday = new Weekday(); public static final Weekday Sunday = new Weekday();}class Employees{ private Weekday restday; //一周的哪一天休息（数据类型为Weekday） public Weekday getRestday() { return restday; } public void setRestday(Weekday restday) //数据类型为Weekday { this.restday = restday; }}public class EnumerateDemo{ public static void main(String[] args) { Employees e = new Employees(); //创建员工对象 e.setRestday(Weekday.Wednesday); //通过类名.对象的方式来设置休息时间 Weekday restday = e.getRestday(); //用Weekday类型的变量restday来接收得到的值 if(restday == Weekday.Saturday || restday == Weekday.Sunday) { System.out.println("周末休息..."); } else { System.out.println("周一至周五休息..."); } }}/*解决了的问题：1、数据类型安全了2、数据范围安全了*///--------------------version:4.(引入枚举)---------------------------------//见JAVA枚举（二），该知识点努力更新中... 转载于:https://blog.51cto.com/freshair/2055199