java 过滤器模式_过滤器模式（Filter Pattern）

过滤器模式

一、什么是过滤器模式

??过滤器模式(Filter 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。这种类型的设计模式属于结构型模式，它结合多个标准来获得单一标准。

二、具体实现

1、主要角色

过滤对象：需要过滤的对象。

过滤条件接口：抽象过滤条件的接口。

具体的过滤条件：根据需要实现过滤条件接口的具体过滤条件。

2、代码实现

1、需要过滤的对象

package com.designpattern.filterPattern;

/**

* 过滤的对象

*

* @author zhongtao on 2018/12/12

*/

public class Person {

private String name;

private String gender; //性别

private int age;

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getGender() {

return gender;

}

public void setGender(String gender) {

this.gender = gender;

}

public int getAge() {

return age;

}

public void setAge(int age) {

this.age = age;

}

public Person(String name, String gender, int age) {

this.name = name;

this.gender = gender;

this.age = age;

}

public Person() {

}

@Override

public String toString() {

return "Person{" +

"name='" + name + ''' +

", gender='" + gender + ''' +

", age=" + age +

'}';

}

}

2、过滤条件接口

package com.designpattern.filterPattern;

import java.util.List;

/**

* 过滤条件接口

*

* @author zhongtao on 2018/12/12

*/

public interface FilterCriteria {

List filterCriteria(List persons);

}

3、具体过滤条件 实现过滤条件接口

package com.designpattern.filterPattern;

import java.util.List;

import java.util.Objects;

import java.util.stream.Collectors;

/**

* 过滤男性

*

* @author zhongtao on 2018/12/12

*/

public class MaleFilter implements FilterCriteria {

@Override

public List filterCriteria(List persons) {

//通过流来处理

return persons.stream().filter(person -> Objects.equals(person.getGender(), "MALE")).collect(Collectors.toList());

}

}

package com.designpattern.filterPattern;

import java.util.List;

import java.util.stream.Collectors;

/**

* 年龄大于20

*

* @author zhongtao on 2018/12/12

*/

public class AgeGreaterThan20Filter implements FilterCriteria {

@Override

public List filterCriteria(List persons) {

return persons.stream().filter(person -> person.getAge() > 20).collect(Collectors.toList());

}

}

package com.designpattern.filterPattern;

import java.util.List;

import java.util.Objects;

import java.util.stream.Collectors;

/**

* 过滤男性并且年龄大于20

*

* @author zhongtao on 2018/12/12

*/

public class MaleAndAgeGreaterThan20Filter implements FilterCriteria {

@Override

public List filterCriteria(List persons) {

return persons.stream().filter(person -> Objects.equals(person.getGender(), "MALE"))

.filter(person -> person.getAge() > 20)

.collect(Collectors.toList());

}

}

4、测试过滤器模式

package com.designpattern.filterPattern;

import org.junit.Test;

import java.util.ArrayList;

import java.util.List;

/**

* @author zhongtao on 2018/12/12

*/

public class FilterPatternTest {

/**

* 测试过滤器模式

*/

@Test

public void testFilterPattern() {

List persons = new ArrayList<>();

persons.add(new Person("Peter", "MALE", 24));

persons.add(new Person("Mary", "FEMALE", 22));

persons.add(new Person("Bob", "MALE", 18));

persons.add(new Person("Lina", "FEMALE", 20));

persons.add(new Person("Luna", "FEMALE", 21));

FilterCriteria maleFilter = new MaleFilter();

List males = maleFilter.filterCriteria(persons);

System.out.println("男的：" + males);

FilterCriteria ageGreaterThan20 = new AgeGreaterThan20Filter();

List ageThan20 = ageGreaterThan20.filterCriteria(persons);

System.out.println("年龄大于20的人：" + ageThan20);

FilterCriteria maleAndAgeGreaterThan20 = new MaleAndAgeGreaterThan20Filter();

List personList = maleAndAgeGreaterThan20.filterCriteria(persons);

System.out.println("男的且年龄大于20的人：" + personList);

}

}

5、测试结果

男的：[Person{name='Peter', gender='MALE', age=24}, Person{name='Bob', gender='MALE', age=18}]

年龄大于20的人：[Person{name='Peter', gender='MALE', age=24}, Person{name='Mary', gender='FEMALE', age=22}, Person{name='Luna', gender='FEMALE', age=21}]

男的且年龄大于20的人：[Person{name='Peter', gender='MALE', age=24}]