This program for writing a program to sort the employee by name and age using JDK 8. Java 8 introduced many out of box features for developers. The comparator in java 8 is marked as @FunctionalInterface, and it provide a cleaner way to develop your code. We had already discussed how the Comparator<T> interface works before java 8. In this post, we will use the stream api with comparator.
Employee.java
package com.javadevelopersguide.lab.basic;
/**
* @author manoj.bardhan
*
*/
public class Employee {
private String name;
private int age;
private String department;
public Employee(String name, int age, String department) {
super();
this.name = name;
this.age = age;
this.department = department;
}
@Override
public String toString() {
return "\n Employee [name=" + name + ", age=" + age + ", department=" + department + "]";
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getDepartment() {
return department;
}
public void setDepartment(String department) {
this.department = department;
}
}
Now we will create an action or main method to use the above POJA class for sorting.
SortEmployeeWithStream.java
package com.javadevelopersguide.lab.basic;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.stream.Collectors;
/**
* This program illustrates sort custom fields using JDK 8 (Stream & Comparator)
*
* @author manoj.bardhan
*
*/
public class SortEmployeeWithStream {
public static void main(String[] args) {
Employee1 e1 = new Employee1("Ander Koli", 32, "Sales");
Employee1 e2 = new Employee1("Andrew Smith", 23, "Sales");
Employee1 e3 = new Employee1("David Jone", 52, "Sales");
Employee1 e4 = new Employee1("Cuba Station", 23, "Marketing");
Employee1 e5 = new Employee1("Bradley Head", 23, "Marketing");
Employee1 e6 = new Employee1("Peter Parker", 34, "Sales");
// Create an arraylist and add all the employee object into that list.
ArrayList<Employee1> employeeList = new ArrayList<Employee1>();
employeeList.add(e1);
employeeList.add(e2);
employeeList.add(e3);
employeeList.add(e4);
employeeList.add(e5);
employeeList.add(e6);
System.out.println("Employee list before sorting -\n" + employeeList);
ArrayList<Employee1> sortedList = (ArrayList) employeeList.stream()
.sorted(Comparator.comparing(Employee1::getName).thenComparing(Employee1::getAge))
.collect(Collectors.toList());
System.out.println("Employee list after sorting -\n" + sortedList);
}
}
Output-
Employee list before sorting -
[
Employee1 [name=Ander Koli, age=32, department=Sales],
Employee1 [name=Andrew Smith, age=23, department=Sales],
Employee1 [name=David Jone, age=52, department=Sales],
Employee1 [name=Cuba Station, age=23, department=Marketing],
Employee1 [name=Bradley Head, age=23, department=Marketing],
Employee1 [name=Peter Parker, age=34, department=Sales]]
Employee list after sorting -
[
Employee1 [name=Ander Koli, age=32, department=Sales],
Employee1 [name=Andrew Smith, age=23, department=Sales],
Employee1 [name=Bradley Head, age=23, department=Marketing],
Employee1 [name=Cuba Station, age=23, department=Marketing],
Employee1 [name=David Jone, age=52, department=Sales],
Employee1 [name=Peter Parker, age=34, department=Sales]]
The Comparator.comparing and thenComparing two static methods inside Comparator. As we know Comparator is a Functional interface which provides default and static methods along with implementation. These functional interfaces are giving out of box functionality. See how before java 8 with Comparator interface examples.
Also we can achieve the above sorting by creating multiple different comparators , which we can use when we need.
We have created two comparator as compareByAge, CompareByDept . Now we can use those comparators at any place we need along with stream. Below sample code snippet shows the usages. Read these reference documents for more about stream, comparator, functions, jdk 8 features.
Comparator<Employee1> compareByAge = Comparator.comparing(Employee1::getAge);
Comparator<Employee1> compareByDept = Comparator.comparing(Employee1::getDepartment);
ArrayList<Employee1> sortedList = (ArrayList) employeeList.stream()
.sorted(compareByAge.thenComparing(compareByDept)).collect(Collectors.toList());
Happy Learning.
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