Java过滤器模式(条件模式)

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过滤器模式或条件模式是一种设计模式,使开发人员可以使用不同的条件过滤一组对象,并通过逻辑操作以解耦方式将其链接…

过滤器模式或条件模式是一种设计模式,使开发人员可以使用不同的条件过滤一组对象,并通过逻辑操作以解耦方式将其链接。 这种类型的设计模式属于结构模式,因为该模式组合多个标准以获得单个标准。

实现实现

我们将创建一个Person对象,Criteria接口和具体类,实现这个接口来过滤Person对象的列表。CriteriaPatternDemo是一个演示类,使用Criteria对象基于各种标准及其组合过滤拥有Person对象的列表(List)。

示例的结构图如下 –

Java过滤器模式(条件模式)

第1步

创建要应用标准的类。

Person.java

public 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;     }      }  

第2步

创建Criteria的接口。

Criteria.java

import java.util.List;    public interface Criteria {     public List<Person> meetCriteria(List<Person> persons);  }  

第3步

创建实现Criteria接口的具体类。

CriteriaMale.java

import java.util.ArrayList;  import java.util.List;    public class CriteriaMale implements Criteria {       @Override     public List<Person> meetCriteria(List<Person> persons) {        List<Person> malePersons = new ArrayList<Person>();           for (Person person : persons) {           if(person.getGender().equalsIgnoreCase("MALE")){              malePersons.add(person);           }        }        return malePersons;     }  }  

CriteriaFemale.java

import java.util.ArrayList;  import java.util.List;    public class CriteriaFemale implements Criteria {       @Override     public List<Person> meetCriteria(List<Person> persons) {        List<Person> femalePersons = new ArrayList<Person>();           for (Person person : persons) {           if(person.getGender().equalsIgnoreCase("FEMALE")){              femalePersons.add(person);           }        }        return femalePersons;     }  }  

CriteriaSingle.java

import java.util.ArrayList;  import java.util.List;    public class CriteriaSingle implements Criteria {       @Override     public List<Person> meetCriteria(List<Person> persons) {        List<Person> singlePersons = new ArrayList<Person>();           for (Person person : persons) {           if(person.getMaritalStatus().equalsIgnoreCase("SINGLE")){              singlePersons.add(person);           }        }        return singlePersons;     }  }  

AndCriteria.java

import 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 List<Person> meetCriteria(List<Person> persons) {          List<Person> firstCriteriaPersons = criteria.meetCriteria(persons);                return otherCriteria.meetCriteria(firstCriteriaPersons);     }  }  

OrCriteria.java

import 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 List<Person> meetCriteria(List<Person> persons) {        List<Person> firstCriteriaItems = criteria.meetCriteria(persons);        List<Person> otherCriteriaItems = otherCriteria.meetCriteria(persons);          for (Person person : otherCriteriaItems) {           if(!firstCriteriaItems.contains(person)){              firstCriteriaItems.add(person);           }        }            return firstCriteriaItems;     }  }  

第4步

使用不同的条件及其组合过滤掉人。

CriteriaPatternDemo.java

public class CriteriaPatternDemo {     public static void main(String[] args) {        List<Person> persons = new ArrayList<Person>();          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(List<Person> persons){          for (Person person : persons) {           System.out.println("Person : [ Name : " + person.getName() + ", Gender : " + person.getGender() + ", Marital Status : " + person.getMaritalStatus() + " ]");        }     }        }  

第5步

验证输出结果,执行上面的代码得到结果如下 –

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 ]  

  

拾荒的老头

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