JAVA枚举与设计模式.ppt

Java枚举与程序设计,作者：李金峰,枚举 单例模式 责任链模式,1.1一个枚举的小例子,package com.li; public enum WeeKDay MON,TUS,WED,THI,FRI,SAT,SUN; ,1.2枚举概述,关键字enum可以将一组具名的值的有限集合创作成一种新的类型，而这种具名的值可以作为常规的组件使用,1.3 基本函数,valueOf(); name(); Ordinal(); toString();,1.4静态导入,package com.li; import static com.li.WeekDay1.*; public class TestStaticImport public static void main(String args) System.out.println(MON); ,1.5.1向enum中添加新方法1,public enum WeekDay2 MON(1), TUS, WED, THI(4), FRI, SAT, SUN; private int value; private WeekDay2() private WeekDay2(int value)this.value = value; public int getValue() return this.value; ,1.5.2向enum中添加新方法2,public enum WeekDay3 MON(“Monday“), TUS(“Tuesday“), WED(“Wednesday“), THI(“Thursday“), FRI( “Friday“), SAT(“Saturday“), SUN(“Sunday“); private String week; private WeekDay3(String week) this.week = week; public String getWeek() return this.week; ,1.6覆盖toString()方法,public enum WeekDay5 MON, TUS, WED, THI, FRI, SAT, SUN; public String toString() return name().toLowerCase(); ,1.6实现,public enum WeekDay6 implements Operate MON, TUS, WED, THI, FRI, SAT, SUN; Override public String doSomething() / TODO Auto-generated method stub return null; ,1.7随机选取,public class Enums private static Random rand = new Random(47); public static T random(Class cl) return random(cl.getEnumConstants(); public static T random(T values) return valuesrand.nextInt(values.length); ,枚举 单例模式 责任链模式,2 单例模式,由于枚举的构造函数必须是私有的，所以用它实现单例模式非常简单。,2.1单例实现1,public enum Singleton INSTANCE; private String name; public String getName() return name; public void setName(String name) = name; public static void main(String args) INSTANCE.setName(“DS“); System.out.println(INSTANCE.getName(); ,2.2单例实现2,public enum Singleton1 RED(255, 0, 0), GREEN(0, 255, 0), BLUE(0, 0, 255); int redValue; int greenValue; int blueValue; private Singleton1(int red,int green,int blue) this.redValue = red; this.greenValue = green; this.blueValue = blue; public int getRedValue() return redValue; public void setRedValue(int red) this.redValue = red; public int getGreenValue() return greenValue; public void setGreenValue(int green) this.greenValue = green; public int getBlueValue() return blueValue; public void setBlueValue(int blue) this.blueValue = blue; public static void main(String args) System.out.println(Singleton1.RED.getRedValue(); ,枚举 单例模式 责任链模式,3 责任链模式,责任链（Chain of Responsibility)是以多种不同的方式来解决问题，然后把他们链到一起。当一个请求来时，它遍历这个链，直到链中的某个解决方案能处理该请求。 下面以新入职员工经历的三方面考核为例。 考核一：面试 60分以下 NO 考核二：笔试 60分以下 NO 考试三：绩效 60分以下 NO 每个员工都要经历这三个过程，一项不合格，拒绝转正。,3.1绩效代码,package com.li.thinking.chain; import java.util.Iterator; public class Performance enum Audition NO, YES1, YES2, YES3, YES4; enum Exam NO, YES1, YES2, YES3, YES4; enum Perform NO, YES1, YES2, YES3, YES4; Audition audition; Exam exam; Perform perform; static long count = 0; long id = count+; public String toString() return “Performance “ + id; public boolean check(Object o) if (o.equals(“NO“) return false; return true; public String getDetails() String result = toString() + “ Audition:“ + audition + “ Exam:“ + exam + “ Perform:“ + perform; if (result.indexOf(“NO“) 0) result += “ -Sorry,you are failed!“; else result += “ -You are successfull!“; return result; public static Performance randomPerformance() Performance p = new Performance(); p.audition = Enums.random(Audition.class); p.exam = Enums.random(Exam.class); p.perform = Enums.random(Perform.class); return p; public static Iterable generator(final int count) return new Iterable() int n = count; public Iterator iterator() return new Iterator() Override public boolean hasNext() / TODO Auto-generated method stub return n- 0; Override public Performance next() / TODO Auto-generated method stub return randomPerformance(); Override public void remove() throw new UnsupportedOperationException(); ; ; ,3.2评审代码,package com.li.thinking.chain; public class ReView enum PerformanceHandler Audition boolean handle(Performance p) switch (p.audition) case NO: return false; default: return true; , Exam boolean handle(Performance p) switch (p.audition) case NO: return false; default: return true; , Perform boolean handle(Performance p) switch (p.audition) case NO: return false; default: return true; ; abstract boolean handle(Performance p); static void handle(Performance p) for (Perfor