過濾器模式允許開發人員使用不同的標準來過濾一組對象，通過邏輯運算以解耦的方式把它們連接起來

實現

創建一個Person對象、Criteria 接口和實現了該接口的實體類，來過濾 Person 對象的列表。CriteriaPatternDemo，我們的演示類使用 Criteria 對象，基于各種標準和它們的結合來過濾 Person 對象的列表。

創建一個Person類

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;

}

}

為標準創建一個接口

import java.util.List;

public interface Criteria {

public List meetCriteria(List persons);

}

創建實體類

創建CriteriaMale類

import java.util.ArrayList;

import java.util.List;

public class CriteriaMale implements Criteria {

@Override

public List meetCriteria(List persons) {

List malePersons = new ArrayList();

for (Person person : persons) {

if(person.getGender().equalsIgnoreCase("MALE")){

malePersons.add(person);

}

}

return malePersons;

}

}

創建CriteriaFemale類

import java.util.ArrayList;

import java.util.List;

public class CriteriaFemale implements Criteria {

@Override

public List meetCriteria(List persons) {

List femalePersons = new ArrayList();

for (Person person : persons) {

if(person.getGender().equalsIgnoreCase("FEMALE")){

femalePersons.add(person);

}

}

return femalePersons;

}

}

創建CriteriaSingle類

import java.util.ArrayList;

import java.util.List;

public class CriteriaSingle implements Criteria {

@Override

public List meetCriteria(List persons) {

List singlePersons = new ArrayList();

for (Person person : persons) {

if(person.getMaritalStatus().equalsIgnoreCase("SINGLE")){

singlePersons.add(person);

}

}

return singlePersons;

}

}

創建AndCriteria類

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 meetCriteria(List persons) {

List firstCriteriaPersons = criteria.meetCriteria(persons);

return otherCriteria.meetCriteria(firstCriteriaPersons);

}

}

創建OrCriteria類

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 meetCriteria(List persons) {

List firstCriteriaItems = criteria.meetCriteria(persons);

List otherCriteriaItems = otherCriteria.meetCriteria(persons);

for (Person person : otherCriteriaItems) {

if(!firstCriteriaItems.contains(person)){

firstCriteriaItems.add(person);

}

}

return firstCriteriaItems;

}

}

使用示例

import java.util.ArrayList;

import java.util.List;

public class CriteriaPatternDemo {

public static void main(String[] args) {

List persons = 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(List persons){

for (Person person : persons) {

System.out.println("Person : [ Name : " + person.getName()

+", Gender : " + person.getGender()

+", Marital Status : " + person.getMaritalStatus()

+" ]");

}

}

}

輸出結果

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 ]

總結

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