什么是过滤器模式？

过滤器模式（Filter Pattern）又称作标准模式（Criteria Pattern），这种模式允许开发人员使用不同的标准来过滤一组对象，通过逻辑运算以解耦的方式把它们连接起来。
过滤器模式就像是一连串的过滤器，按条件或标准筛选一组对象出来。
适用场景

需要按条件筛选对象的场景都可以使用过滤器模式。
代码实现

示例：找对象
假设要求：白富美 18-23岁女性
//示例： 找对象
//假设要求：白富美 18-23岁 女性
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
/**
 * 人类
 */
class Person {
    private String name;//姓名
    private int age;//年龄
    private String gender;//性别
    private String skinColour;//肤色
    private String riches;//财富
    private String looks;//长相
    public Person(String name, int age, String gender, String skinColour, String riches, String looks) {
        this.name = name;
        this.age = age;
        this.gender = gender;
        this.skinColour = skinColour;
        this.riches = riches;
        this.looks = looks;
    }
    @Override
    public String toString() {
        return
                "姓名：" + name +
                        "， 年龄：" + age +
                        "， 性别：" + gender +
                        "， 肤色：" + skinColour +
                        "， 财富：" + riches +
                        "， 长相：" + looks;
    }
    //region IDEA折叠代码
    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;
    }
    public String getGender() {
        return gender;
    }
    public void setGender(String gender) {
        this.gender = gender;
    }
    public String getSkinColour() {
        return skinColour;
    }
    public void setSkinColour(String skinColour) {
        this.skinColour = skinColour;
    }
    public String getRiches() {
        return riches;
    }
    public void setRiches(String riches) {
        this.riches = riches;
    }
    public String getLooks() {
        return looks;
    }
    public void setLooks(String looks) {
        this.looks = looks;
    }
    //endregion
}
/**
 * 过滤器
 */
interface Filter {
    List<Person> filter(List<Person> persons);
}
/**
 * 过滤年龄
 * 要18-23岁
 */
class AgeFilter implements Filter {
    @Override
    public List<Person> filter(List<Person> persons) {
        return persons
                .stream()
                .filter(person -> person.getAge() >= 18 && person.getAge() < +23)
                .collect(Collectors.toList());
    }
}
/**
 * 过滤性别
 * 要女性
 */
class GenderFilter implements Filter {
    @Override
    public List<Person> filter(List<Person> persons) {
        return persons
                .stream()
                .filter(person -> person.getGender().equals("女性"))
                .collect(Collectors.toList());
    }
}
/**
 * 过滤肤色，要白色
 */
class SkinColourFilter implements Filter {
    @Override
    public List<Person> filter(List<Person> persons) {
        return persons
                .stream()
                .filter(person -> person.getSkinColour().equals("白色"))
                .collect(Collectors.toList());
    }
}
/**
 * 过滤财富，要富裕
 */
class RichesFilter implements Filter {
    @Override
    public List<Person> filter(List<Person> persons) {
        return persons
                .stream()
                .filter(person -> person.getSkinColour().equals("富裕"))
                .collect(Collectors.toList());
    }
}
/**
 * 过滤长相，要好看
 */
class LooksFilter implements Filter {
    @Override
    public List<Person> filter(List<Person> persons) {
        return persons
                .stream()
                .filter(person -> person.getSkinColour().equals("好看"))
                .collect(Collectors.toList());
    }
}
/**
 * 过滤器模式
 */
public class FilterPattern {
    public static void main(String[] args) {
        //选妃大赛  找对象
        //准备妃子
        List<Person> persons = new ArrayList<>();
        persons.add(new Person("小红", 3, "女", "白色", "富裕", "好看"));
        persons.add(new Person("小蓝", 25, "女", "黄色", "贫穷", "难看"));
        persons.add(new Person("小绿", 5, "男", "白色", "富裕", "好看"));
        persons.add(new Person("小白", 56, "女", "白色", "贫穷", "好看"));
        persons.add(new Person("小橙", 35, "女", "黄色", "富裕", "好看"));
        persons.add(new Person("小黄", 12, "男", "黑色", "贫穷", "难看"));
        persons.add(new Person("小青", 23, "女", "黄色", "富裕", "好看"));
        persons.add(new Person("小丹", 18, "女", "白色", "贫穷", "好看"));
        persons.add(new Person("小紫", 16, "男", "白色", "贫穷", "难看"));
        persons.add(new Person("小粉", 17, "女", "黄色", "富裕", "好看"));
        persons.add(new Person("小褐", 19, "女", "白色", "贫穷", "难看"));
        persons.add(new Person("小棕", 20, "女", "黄色", "富裕", "难看"));
        persons.add(new Person("小黑", 43, "男", "白色", "贫穷", "好看"));
        persons.add(new Person("小灰", 91, "女", "黑色", "贫穷", "难看"));
        persons.add(new Person("小暗", 32, "女", "白色", "富裕", "好看"));
        persons.add(new Person("小亮", 56, "女", "黑色", "贫穷", "难看"));
        //过滤器
        AgeFilter ageFilter = new AgeFilter();
        GenderFilter genderFilter = new GenderFilter();
        SkinColourFilter skinColourFilter = new SkinColourFilter();
        RichesFilter richesFilter = new RichesFilter();
        LooksFilter looksFilter = new LooksFilter();
        //层层选拔
        System.out.println("选拨前人数：" + persons.size());
        persons = ageFilter.filter(persons);
        System.out.println("过滤年龄后人数：" + persons.size());
        persons = genderFilter.filter(persons);
        System.out.println("过滤性别后人数：" + persons.size());
        persons = skinColourFilter.filter(persons);
        System.out.println("过滤肤色后人数：" + persons.size());
        persons = richesFilter.filter(persons);
        System.out.println("过滤富裕后人数：" + persons.size());
        persons = looksFilter.filter(persons);
        System.out.println("过滤长相后人数：" + persons.size());
        //输出：
        //选拨前人数：16
        //过滤年龄后人数：3
        //过滤性别后人数：0
        //过滤肤色后人数：0
        //过滤富裕后人数：0
        //过滤长相后人数：0
        //打光棍吧  没找到 ……
    }
}
编程指南

过滤器模式 Filter Pattern

什么是过滤器模式？

适用场景

代码实现
