23种设计模式之过滤模式
/** * 1.模式定义: * 过滤器(Filter Pattern)又称为标准模式(Criteria Pattern)是一种设计模式,这种模式允许开发人员使用不同的标准来过滤一组对象, * 通过预算逻辑以解耦的方式将他们联系起来。这种类型的设计模式属于结构模型,说白了,就是按条件筛选一组对象出来。 * 目的:使用不同标准来过滤一组对象 * 实现:制定不同的规则来实现过滤,然后对过滤结果进行分组。 * 2.组成角色: * 1)抽象过滤器角色(AbstractFilter):负责定义过滤器的实现接口,具体的实现还要具体过滤器角色去参与,客户端可以调用抽象过滤器角色中定义好 * 的方法,将 客户端的所有请求委派到具体的实现类去,从而让实现类去处理。 * 2)ConcreteFilter(具体过滤角色):该角色负责具体筛选规则的逻辑实现,最后再返回一个过滤后的数据集合,标准的过滤器只对数据做过滤,当然也 * 可以对集合中的数据做某项处理,再将处理后的集合返回。 * 3)Subject(被过滤的主体角色):一个软件系统中可以有一个或多个目标角色,在具体过滤器角色中对指定的目标进行处理。 * 3.过滤器延伸: * 过滤器链:携带多个过滤器,并且可以以自定义顺序执行他们。 * 过滤器管理角色:负责管理过滤器和过滤器链。 * 4.应用场景: * 垃圾桶分类 * 5.总结: * 1)可插拔:过滤器的设计概念要求其实支持可插拔设计的。 * 2)有序性:过滤器是被设计为一组组的过滤装置,要实现数据过滤,就必须有序性要求. * 3)过滤器的独立性:每种过滤器必须是独立的实体,其状态不受其它过滤器的影响,每个过滤器都有自己独立的数据输入输出接口,只要各个过滤器之间 * 传送的数据遵守共同的规约就可以相连接。 */ /* * 垃圾類,被過濾的主題角色 */ public class Rubbish { private String name; //垃圾名稱 private boolean isHarm; //是否有害垃圾 private boolean isRecycled; //是否可回收 private boolean isDry; //是否干垃圾 private boolean isWet; //是否湿垃圾 public Rubbish(String name, boolean isHarm, boolean isRecycled, boolean isDry, boolean isWet) { this.name = name; this.isHarm = isHarm; this.isRecycled = isRecycled; this.isDry = isDry; this.isWet = isWet; } public String getName() { return name; } public void setName(String name) { this.name = name; } public boolean isHarm() { return isHarm; } public void setHarm(boolean isHarm) { this.isHarm = isHarm; } public boolean isRecycled() { return isRecycled; } public void setRecycled(boolean isRecycled) { this.isRecycled = isRecycled; } public boolean isDry() { return isDry; } public void setDry(boolean isDry) { this.isDry = isDry; } public boolean isWet() { return isWet; } public void setWet(boolean isWet) { this.isWet = isWet; } } /* * 过滤标准的接口,即抽象过滤角色 */ public interface Criteria { //定义过滤的标准 List<Rubbish> rubbishFilter(List<Rubbish> rubbishs); } /* * 实现Criteria接口的实体类 */ //干垃圾 public class DryRubbishCriteria implements Criteria { @Override public List<Rubbish> rubbishFilter(List<Rubbish> rubbishs) { List<Rubbish> rubbishList=new ArrayList<Rubbish>(); for(Rubbish rubbish:rubbishs) { //这里只过滤出所有干垃圾 if (rubbish.isDry()) { rubbishList.add(rubbish); } } return rubbishList; } } //有害垃圾 public class HarmfulRubbishCriteria implements Criteria { @Override public List<Rubbish> rubbishFilter(List<Rubbish> rubbishs) { List<Rubbish> rubbishList=new ArrayList<Rubbish>(); for(Rubbish rubbish:rubbishs) { //这里只过滤出所有干垃圾 if (rubbish.isHarm()) { rubbishList.add(rubbish); } } return rubbishList; } } //可回收垃圾 public class RecycledRubbishCriteria implements Criteria{ @Override public List<Rubbish> rubbishFilter(List<Rubbish> rubbishs) { List<Rubbish> rubbishList=new ArrayList<Rubbish>(); for(Rubbish rubbish:rubbishs) { //这里只过滤出所有干垃圾 if (rubbish.isRecycled()) { rubbishList.add(rubbish); } } return rubbishList; } } //湿垃圾 public class WetRubbishCriteria implements Criteria{ @Override public List<Rubbish> rubbishFilter(List<Rubbish> rubbishs) { List<Rubbish> rubbishList=new ArrayList<Rubbish>(); for(Rubbish rubbish:rubbishs) { //这里只过滤出所有干垃圾 if (rubbish.isWet()) { rubbishList.add(rubbish); } } return rubbishList; } }
测试结果如下:
//使用不同的标准(Criteria)来过滤Rubbish对象的列表 public class Main { public static void main(String[] args) { //原始数据集合 List<Rubbish> rubbishList = new ArrayList<Rubbish>(); rubbishList.add(new Rubbish("果壳", false, false, true, false)); rubbishList.add(new Rubbish("陶瓷", false, false, true, false)); rubbishList.add(new Rubbish("菜根菜叶", false, false, false, true)); rubbishList.add(new Rubbish("果皮", false, false, false, true)); rubbishList.add(new Rubbish("电池", true, false, false, false)); rubbishList.add(new Rubbish("水银温度计", true, false, false, false)); rubbishList.add(new Rubbish("灯泡", true, false, false, false)); rubbishList.add(new Rubbish("废纸塑料", false, true,false, false)); rubbishList.add(new Rubbish("金属和布料", false, true, false, false)); //四种不同的过滤标准 Criteria dryRubbishCriteria=new DryRubbishCriteria(); Criteria wetRubbishCriteria=new WetRubbishCriteria(); Criteria harRubbishCriteria=new HarmfulRubbishCriteria(); Criteria recycledRubbishCriteria=new RecycledRubbishCriteria(); System.out.println("干垃圾:"); printRubbishes(dryRubbishCriteria.rubbishFilter(rubbishList)); System.out.println("湿垃圾:"); printRubbishes(wetRubbishCriteria.rubbishFilter(rubbishList)); System.out.println("有害垃圾:"); printRubbishes(harRubbishCriteria.rubbishFilter(rubbishList)); System.out.println("可回收垃圾:"); printRubbishes(recycledRubbishCriteria.rubbishFilter(rubbishList)); } private static void printRubbishes(List<Rubbish> rubbishs) { for(Rubbish rubbish:rubbishs) { System.out.println(rubbish.getName()); } } } 干垃圾: 果壳 陶瓷 湿垃圾: 菜根菜叶 果皮 有害垃圾: 电池 水银温度计 灯泡 可回收垃圾: 废纸塑料 金属和布
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