Java Filter mode (Filter/criteria pattern) Detailed introduction _java

Java Filter mode (Filter/criteria pattern)

Filter pattern or Standard mode (criteria pattern) is a design pattern that allows developers to filter a set of objects using different criteria and connect them in a decoupled way by logical operation. This type of design pattern is a structured pattern that combines multiple criteria to achieve a single standard.

Filter pattern or Standard mode (criteria pattern) is a design pattern that allows developers to filter a set of objects using different criteria and connect them in a decoupled way by logical operation. This type of design pattern is a structured pattern that combines multiple criteria to achieve a single standard.

Realize

We will create a person object, a Criteria interface, and an entity class that implements the interface to filter the list of person objects. Criteriapatterndemo, our demo class uses the criteria object to filter the list of person objects based on various criteria and their combination.

Step 1

Create a class that applies a standard on that class.

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
  }}  

Step 2

Create an interface for the criteria (criteria).

Criteria.java

Import java.util.List;
 
Public interface The Criteria {public
  list<person> Meetcriteria (list<person> persons);
}
 

Step 3

Creates an entity class that implements the Criteria interface.

Criteriamale.java

Import java.util.ArrayList;
Import java.util.List;
 
public class Criteriamale implements the 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 the 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 the 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
      ) { Firstcriteriaitems.add (person);
     }
   Return Firstcriteriaitems
  }
}

Step 4

Filter the list of person objects using different criteria (criteria) and their combination.

Criteriapatterndemo.java

public class Criteriapatterndemo {public static void main (string[] args) {list<person> persons = new Arrayli
 
   St<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 ("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.prin TLN ("Person: [Name:" + person.getname () + ", Gender:" + person.getgender () + ", Marital Status:" + Perso
   N.getmaritalstatus () + "]");
 

 }
  }   
}

Step 5

Verify the output.

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:mal E, marital status:single] Females:person: [Name:laura, Gender:female, marital status:married] Person: [Na Me:diana, Gender:female, marital status:single] single males:person: [Name:robert, Gender:male, Marital St Atus:single] Person: [Name:mike, Gender:male, marital status:single] Person: [Name:bobby, Gender:male, M Arital 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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