设计模式之过滤器模式

意图

使用一系列的标准过滤一组对象

实现

创建过滤对象的实体类

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;
    }
}

创建过滤器接口

public interface Criteria {
    List<Person> meetCriteria(List<Person> personList);
}

实现过滤器接口

public class FemaleCriteria implements Criteria {
    @Override
    public List<Person> meetCriteria(List<Person> personList) {
        List<Person> female = new ArrayList<>();
        for(Person person : personList) {
            if (person.getGender().equalsIgnoreCase("FEMALE"))
                female.add(person);
        }
        return female;
    }
}

public class MaleCriteria implements Criteria {
    @Override
    public List<Person> meetCriteria(List<Person> personList) {
        List<Person> male = new ArrayList<>();
        for (Person person : personList) {
            if (person.getGender().equalsIgnoreCase("MALE"))
                male.add(person);
        }
        return male;
    }
}

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

public class OrCriteria implements Criteria {
    private Criteria criteria;
    private Criteria otherCriteria;

    public OrCriteria(Criteria criteria, Criteria otherCriteria) {
        this.criteria = criteria;
        this.otherCriteria = criteria;
    }

    @Override
    public List<Person> meetCriteria(List<Person> personList) {
        List<Person> firstCriteriaPerson = criteria.meetCriteria(personList);
        List<Person> otherCriteriaPerson = criteria.meetCriteria(personList);

        for (Person person : firstCriteriaPerson) {
            if (!otherCriteriaPerson.contains(person))
                otherCriteriaPerson.add(person);
        }
        return otherCriteriaPerson;
    }
}

测试

public class FilterPatternDemo {
    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 MaleCriteria();
        Criteria female = new FemaleCriteria();
        Criteria single =  new SingleCriteria();
        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()
                    +" ]");
        }
    }
}

结果

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 ]