Java Functional Interfaces – Consumer & BiConsumer
This section describes the functional interfaces Consumer & BiConsumer defined in java.util.Function package in Java 8.
What is it?
public interface Consumer<T>
{
void accept(T t) ;
}
public interface BiConsumer<T,U>
{
void accept(T t, U u);
}
When should you use it?
Examples
The examples illustrated below use the following Employee POJO class:
|
package org.examples;
public class Employee { private String name; private Integer hourRate; public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getHourRate() { return hourRate; } public void setHourRate(Integer hourRate) { this.hourRate = hourRate; } public Employee(String name, Integer hourRate) { super(); this.name = name; this.hourRate = hourRate; } @Override public String toString() { return “Employee [name=” + name + “, hourRate=” + hourRate + “]”; } } |
|
package org.examples;
package org.examples;
import java.util.Arrays; import java.util.List; import java.util.function.Consumer;
public class ConsumerExample1 { public static void main(String[] args) { List<Employee> employees = Arrays.asList(new Employee(“Jack”, 10), new Employee(“Robert”, 50), new Employee(“David”, 30), new Employee(“Abhi”, 20)); employeeConsumer(employees, print());
}
public static Consumer<Employee> print() { Consumer<Employee> consumer = emp -> System.out.println(“Rate of “ + emp.getName() + ” is $” + emp.getHourRate() + ” per hour.”); return consumer; }
public static void employeeConsumer (List<Employee> employees, Consumer<Employee> consumer) { for(Employee emp : employees) { consumer.accept(emp); } } }
|
|
Output: Rate of Jack is $10 per hour. Rate of Robert is $50 per hour. Rate of David is $30 per hour. Rate of Abhi is $20 per hour. |
|
package org.examples;
package org.examples;
import java.util.Arrays; import java.util.List; import java.util.function.Consumer;
public class ConsumerExample2 { public static void main(String[] args) { List<Employee> employees = Arrays.asList(new Employee(“Jack”, 10), new Employee(“Robert”, 50), new Employee(“David”, 30), new Employee(“Abhi”, 20)); employees.forEach(print()); }
public static Consumer<Employee> print() { Consumer<Employee> consumer = emp -> System.out.println(“Rate of “ + emp.getName() + ” is $” + emp.getHourRate() + ” per hour.”); return consumer; } }
|
|
Output: Rate of Jack is $10 per hour. Rate of Robert is $50 per hour. Rate of David is $30 per hour. Rate of Abhi is $20 per hour. |
|
package org.examples;
import java.util.Arrays; import java.util.List; import java.util.function.Consumer;
public class ConsumerExample3 { public static void main(String[] args) { List<Employee> employees = Arrays.asList(new Employee(“Jack”, 10), new Employee(“Robert”, 50), new Employee(“David”, 30), new Employee(“Abhi”, 20)); employeeConsumer(employees, changeNameCase(), print());
//Alternative method-use forEach with the consumer as input employees.forEach(changeNameCase().andThen(print()));
}
public static Consumer<Employee> print() { Consumer<Employee> consumer = emp -> System.out.println(emp.getName()); return consumer; }
public static Consumer<Employee> changeNameCase() { Consumer<Employee> consumer = emp -> emp.setName(emp.getName().toUpperCase()); return consumer; }
public static void employeeConsumer(List<Employee> employees, Consumer<Employee> consumer1, Consumer<Employee> consumer2) { for(Employee emp : employees) { consumer1.andThen(consumer2).accept(emp); } } } |
|
Output: JACK ROBERT DAVID ABHI |
|
package org.examples;
import java.util.Arrays; import java.util.List; import java.util.function.BiConsumer;
public class BiConsumerExample1 { public static void main(String[] args) { List<Employee> employees = Arrays.asList(new Employee(“Jack”, 10), new Employee(“Robert”, 50), new Employee(“David”, 30), new Employee(“Abhi”, 20));
appendLastName().accept(employees.get(0),“Fernandez”); appendLastName().accept(employees.get(1),“Jones”); appendLastName().accept(employees.get(2),“Beckham”); appendLastName().accept(employees.get(3),“San”); System.out.print(employees); }
public static BiConsumer<Employee,String> appendLastName() { BiConsumer<Employee,String> consumer = (emp,str) -> emp.setName(emp.getName()+” “+str); return consumer; } } |
|
Output: [Employee [name=Jack Fernandez, hourRate=10], Employee [name=Robert Jones, hourRate=50], Employee [name=David Beckham, hourRate=30], Employee [name=Abhi San, hourRate=20]] |
|
package org.examples;
import java.util.Arrays; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.function.BiConsumer;
public class BiConsumerExample2 { public static void main(String[] args) { Map<String,List<Employee>> employees = new HashMap<>(); employees.put(“Admin”, Arrays.asList(new Employee(“Jack”, 10),new Employee(“David”, 30))); employees.put(“Sales”, Arrays.asList(new Employee(“Robert”, 50),new Employee(“Abhi”, 20))); employees.forEach(totalRate()); }
public static BiConsumer<String,List<Employee>> totalRate() { BiConsumer<String,List<Employee>> consumer = (str,list) -> { Integer total = 0; for(Employee emp : list) { total+=emp.getHourRate(); } System.out.println(str + “=” + total); }; return consumer; } } |
|
Output: Sales=70 Admin=40 |
|
package org.examples;
import java.util.Arrays; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.function.BiConsumer;
import java.util.Arrays; import java.util.List; import java.util.function.BiConsumer;
public class BiConsumerExample3 { public static void main(String[] args) { List<Employee> employees = Arrays.asList(new Employee(“Jack”, 10), new Employee(“Robert”, 50), new Employee(“David”, 30), new Employee(“Abhi”, 20));
empConsumer(employees.get(0),employees.get(1), printMaxRate()); empConsumer(employees.get(0),employees.get(1), printTotalRate()); }
public static BiConsumer<Employee,Employee> printTotalRate() { BiConsumer<Employee,Employee> consumer = (emp1,emp2) -> { Integer total = emp1.getHourRate()+emp2.getHourRate(); System.out.println(“Total Rate=”+total); }; return consumer; }
public static BiConsumer<Employee,Employee> printMaxRate() { BiConsumer<Employee,Employee> consumer = (emp1,emp2) -> { if (emp1.getHourRate() > emp2.getHourRate()) { System.out.println(“Max rate=”+emp1.getHourRate()); } else { System.out.println(“Max rate=”+emp2.getHourRate()); } }; return consumer; }
public static void empConsumer(Employee emp1, Employee emp2, BiConsumer<Employee,Employee> consumer) { consumer.accept(emp1, emp2); } } |
|
Output: Max rate=50 Total Rate=60 |
Leave a Reply