Consumer Functional Interface

     Sometimes our requirement is we have to provide some input value, perform certain operation, but not required to return anything,then we should go for Consumer.i.e Consumer can be used to consume object and perform certain operation. Consumer Functional Interface contains one abstract method accept.

interface Consumer<T> { 
   public void accept(T t); 
}

Example

package com.ashok.java8.consumer;

import java.util.function.Consumer;

/**
 * 
 * @author ashok.mariyala
 *
 */
public class ConsumerTest {
   public static void main(String[] args) {
      Consumer<String> c = s -> System.out.println(s);
      c.accept("Ashok Kumar");
   }
}
Output
Ashok Kumar

Display Movie Information by using Consumer

package com.ashok.java8.consumer;

import java.util.ArrayList;
import java.util.List;
import java.util.function.Consumer;

/**
 * 
 * @author ashok.mariyala
 *
 */
public class DisplayMovieNames {
   public static void main(String[] args) {
      List<Movie> list = new ArrayList<>();
      populate(list);
      Consumer<Movie> c = m -> {
         System.out.println("Movie Name : " + m.name);
         System.out.println("Movie Hero : " + m.hero);
         System.out.println("Movie Heroine : " + m.heroine);
         System.out.println();
      };
      
      for(Movie m : list) { 
         c.accept(m); 
      }
   }

   public static void populate(List<Movie> list) {
      list.add(new Movie("Bahubali", "Prabhas", "Anushka"));
      list.add(new Movie("Geetha Govindam", "Vijay Deverakonda", "Rashmika Mandanna"));
      list.add(new Movie("Goodachari", "Adivi Sesh", "Sobhita Dhulipala"));
   }
}

class Movie {
   String name;
   String hero;
   String heroine;

   public Movie(String name, String hero, String heroine) {
      this.name = name;
      this.hero = hero;
      this.heroine = heroine;
   }
}
Output
Movie Name : Bahubali
Movie Hero : Prabhas
Movie Heroine : Anushka

Movie Name : Geetha Govindam
Movie Hero : Vijay Deverakonda
Movie Heroine : Rashmika Mandanna

Movie Name : Goodachari
Movie Hero : Adivi Sesh
Movie Heroine : Sobhita Dhulipala

Consumer Chaining
     Just like Predicate Chaining and Function Chaining, Consumer Chaining is also possible. For this Consumer Functional Interface contains default method andThen().

c1.andThen(c2).andThen(c3).accept(s)

     First Consumer c1 will be applied followed by c2 and c3.
Example 

package com.ashok.java8.consumer;

import java.util.function.Consumer;

/**
 * 
 * @author ashok.mariyala
 *
 */
public class ConsumerChaining {
   public static void main(String[] args) {
      Consumer<MovieResult> c1 = m -> System.out.println("Movie : " + m.name + " is ready to release");
      Consumer<MovieResult> c2 = m -> System.out.println("Movie : " + m.name + " is just Released and it is : " + m.result);
      Consumer<MovieResult> c3 = m -> System.out.println("Movie : " + m.name + " information storing in the database");
      
      Consumer<MovieResult> chainedC = c1.andThen(c2).andThen(c3);
      
      MovieResult m1 = new MovieResult("Bahubali", "Hit");
      chainedC.accept(m1);
      MovieResult m2 = new MovieResult("Spider", "Flop");
      chainedC.accept(m2);
   }
}

class MovieResult {
   String name;
   String result;

   public MovieResult(String name, String result) {
      this.name = name;
      this.result = result;
   }
}
Movie : Bahubali is ready to release
Movie : Bahubali is just Released and it is : Hit
Movie : Bahubali information storing in the database
Movie : Spider is ready to release
Movie : Spider is just Released and it is : Flop
Movie : Spider information storing in the database

Next Tutorial : Supplier Functional Interface

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