过滤器模式
过滤器模式（Filter Pattern）或标准模式（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。
示例演示：
我们创建一个people实体
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15package test.filter;
import lombok.Data;
public class People {
private Integer id;
private String name;
public People(Integer id, String name) {
this.id = id;
this.name = name;
}
}创建一个peopleId的接口，用于通过id对people分组
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7package test.filter;
import java.util.List;
public interface PeopleId {
public List<People> group(List<People> peoples);
}接下来我们按照奇偶对id进行分类，我们创建两个实现类分班对group进行实现
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17package test.filter;
import java.util.ArrayList;
import java.util.List;
public class OddPeople implements PeopleId {
public List<People> group(List<People> peoples) {
List<People> oddPeoples = new ArrayList<>();
for (People people : peoples) {
if (people.getId() % 2 != 0) {
oddPeoples.add(people);
}
}
return oddPeoples;
}
}1
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17package test.filter;
import java.util.ArrayList;
import java.util.List;
public class EvenPeople implements PeopleId {
public List<People> group(List<People> peoples) {
List<People> evenPeoples = new ArrayList<>();
for (People people : peoples) {
if (people.getId() % 2 == 0) {
evenPeoples.add(people);
}
}
return evenPeoples;
}
}完成上述步骤，我们就可以开始演示了
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28package test.filter;
import java.util.ArrayList;
import java.util.List;
public class FilterDemo {
public static void main(String[] args) {
List<People> peoples = new ArrayList<>();
peoples.add(new People(1,"1"));
peoples.add(new People(2,"2"));
peoples.add(new People(3,"3"));
peoples.add(new People(4,"4"));
peoples.add(new People(5,"5"));
peoples.add(new People(6,"6"));
peoples.add(new People(7,"7"));
peoples.add(new People(8,"8"));
peoples.add(new People(9,"9"));
peoples.add(new People(10,"10"));
PeopleId oddPeople = new OddPeople();
System.out.println(oddPeople.group(peoples).toString());
PeopleId evenPeople = new EvenPeople();
System.out.println(evenPeople.group(peoples).toString());
}
}运行结果：
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2[People(id=1, name=1), People(id=3, name=3), People(id=5, name=5), People(id=7, name=7), People(id=9, name=9)]
[People(id=2, name=2), People(id=4, name=4), People(id=6, name=6), People(id=8, name=8), People(id=10, name=10)]说明：
过滤器模式就是我们对一组对象进行过滤，java8提供了里面就提供了很多方法来过滤数据，比如刚才的按照奇偶分类我们就可以直接使用java8提供的方法：
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Map<Integer, List<People>> groupList = peoples.stream().collect(Collectors.groupingBy(c -> c.getId()%2));