Java中过滤器模式有什么用

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实现

我们将创建一个 Person 对象、Criteria 接口和实现了该接口的实体类，来过滤 Person 对象的列表。CriteriaPatternDemo，我们的演示类使用 Criteria 对象，基于各种标准和它们的结合来过滤 Person 对象的列表。

步骤 1

创建一个类，在该类上应用标准。

Person.javapublic class Person {      private String name;   private String gender;   private String maritalStatus;    public Person(String name,String gender,String maritalStatus){      this.name = name;      this.gender = gender;      this.maritalStatus = maritalStatus;       }    public String getName() {      return name;   }   public String getGender() {      return gender;   }   public String getMaritalStatus() {      return maritalStatus;   }  }

步骤 2

为标准（Criteria）创建一个接口。

Criteria.javaimport java.util.List; public interface Criteria {   public ListmeetCriteria(Listpersons);}

步骤 3

创建实现了 Criteria 接口的实体类。

CriteriaMale.javaimport java.util.ArrayList;import java.util.List; public class CriteriaMale implements Criteria {    @Override   public ListmeetCriteria(Listpersons) {      ListmalePersons = new ArrayList();       for (Person person : persons) {         if(person.getGender().equalsIgnoreCase("MALE")){            malePersons.add(person);         }      }      return malePersons;   }}CriteriaFemale.javaimport java.util.ArrayList;import java.util.List; public class CriteriaFemale implements Criteria {    @Override   public ListmeetCriteria(Listpersons) {      ListfemalePersons = new ArrayList();       for (Person person : persons) {         if(person.getGender().equalsIgnoreCase("FEMALE")){            femalePersons.add(person);         }      }      return femalePersons;   }}CriteriaSingle.javaimport java.util.ArrayList;import java.util.List; public class CriteriaSingle implements Criteria {    @Override   public ListmeetCriteria(Listpersons) {      ListsinglePersons = new ArrayList();       for (Person person : persons) {         if(person.getMaritalStatus().equalsIgnoreCase("SINGLE")){            singlePersons.add(person);         }      }      return singlePersons;   }}AndCriteria.javaimport java.util.List; public class AndCriteria implements Criteria {    private Criteria criteria;   private Criteria otherCriteria;    public AndCriteria(Criteria criteria, Criteria otherCriteria) {      this.criteria = criteria;      this.otherCriteria = otherCriteria;    }    @Override   public ListmeetCriteria(Listpersons) {      ListfirstCriteriaPersons = criteria.meetCriteria(persons);           return otherCriteria.meetCriteria(firstCriteriaPersons);   }}OrCriteria.javaimport java.util.List; public class OrCriteria implements Criteria {    private Criteria criteria;   private Criteria otherCriteria;    public OrCriteria(Criteria criteria, Criteria otherCriteria) {      this.criteria = criteria;      this.otherCriteria = otherCriteria;    }    @Override   public ListmeetCriteria(Listpersons) {      ListfirstCriteriaItems = criteria.meetCriteria(persons);      ListotherCriteriaItems = otherCriteria.meetCriteria(persons);       for (Person person : otherCriteriaItems) {         if(!firstCriteriaItems.contains(person)){           firstCriteriaItems.add(person);         }      }        return firstCriteriaItems;   }}

步骤4

使用不同的标准（Criteria）和它们的结合来过滤 Person 对象的列表。

CriteriaPatternDemo.javaimport java.util.ArrayList; import java.util.List; public class CriteriaPatternDemo {   public static void main(String[] args) {      Listpersons = new ArrayList();       persons.add(new Person("Robert","Male", "Single"));      persons.add(new Person("John","Male", "Married"));      persons.add(new Person("Laura","Female", "Married"));      persons.add(new Person("Diana","Female", "Single"));      persons.add(new Person("Mike","Male", "Single"));      persons.add(new Person("Bobby","Male", "Single"));       Criteria male = new CriteriaMale();      Criteria female = new CriteriaFemale();      Criteria single = new CriteriaSingle();      Criteria singleMale = new AndCriteria(single, male);      Criteria singleOrFemale = new OrCriteria(single, female);       System.out.println("Males: ");      printPersons(male.meetCriteria(persons));       System.out.println("\nFemales: ");      printPersons(female.meetCriteria(persons));       System.out.println("\nSingle Males: ");      printPersons(singleMale.meetCriteria(persons));       System.out.println("\nSingle Or Females: ");      printPersons(singleOrFemale.meetCriteria(persons));   }    public static void printPersons(Listpersons){      for (Person person : persons) {         System.out.println("Person : [ Name : " + person.getName()             +", Gender : " + person.getGender()             +", Marital Status : " + person.getMaritalStatus()            +" ]");      }   }      }

步骤 5

执行程序，输出结果：

Males: Person : [ Name : Robert, Gender : Male, Marital Status : Single ]Person : [ Name : John, Gender : Male, Marital Status : Married ]Person : [ Name : Mike, Gender : Male, Marital Status : Single ]Person : [ Name : Bobby, Gender : Male, Marital Status : Single ]Females: Person : [ Name : Laura, Gender : Female, Marital Status : Married ]Person : [ Name : Diana, Gender : Female, Marital Status : Single ]Single Males: Person : [ Name : Robert, Gender : Male, Marital Status : Single ]Person : [ Name : Mike, Gender : Male, Marital Status : Single ]Person : [ Name : Bobby, Gender : Male, Marital Status : Single ]Single Or Females: Person : [ Name : Robert, Gender : Male, Marital Status : Single ]Person : [ Name : Diana, Gender : Female, Marital Status : Single ]Person : [ Name : Mike, Gender : Male, Marital Status : Single ]Person : [ Name : Bobby, Gender : Male, Marital Status : Single ]Person : [ Name : Laura, Gender : Female, Marital Status : Married ]

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