Java 8 Lambda - Java Sort an Array of Objects in Ascending and Descending Order

In this tutorial, we will see how to sort an array of objects in Ascending and descending order using Java 8 Lambda expressions.

Learn Java 8 Lambda at https://www.javaguides.net/2018/07/java-8-lambda-expressions.html

Also, check out Java Sort Array Objects using Comparable Interface.

Check out Comparator example at https://www.javaguides.net/2018/12/java-comparator-interface-example.html

Learn Java Array at https://www.javaguides.net/2020/04/java-array-tutorial-for-beginners.html.

Employee Class

Let's first create an Employee class:

package com.java.array.tutorial.sorting;

public class Employee implements Comparable < Employee > {
    private int id;
    private String name;
    private int salary;


    public Employee(int id, String name, int salary) {
        super();
        this.id = id;
        this.name = name;
        this.salary = salary;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getSalary() {
        return salary;
    }
    public void setSalary(int salary) {
        this.salary = salary;
    }
    @Override
    public String toString() {
        return "Employee [id=" + id + ", name=" + name + ", salary=" + salary + "]";
    }
    @Override
    public int compareTo(Employee o) {
        return this.salary - o.salary;
    }
}

Java 8 Lambda - Sort an Array of Employee objects (by salary) in Ascending Order

The following example sort an array of employee objects in Ascending order:

package com.java.array.tutorial.sorting;

import java.util.Arrays;

public class SortArray {
    public static void main(String[] args) {

        // sort Array of employee objects using Comparator interface

        Employee[] employees = {
            new Employee(10, "Ramesh", 50000),
            new Employee(20, "John", 30000),
            new Employee(30, "tom", 40000),
            new Employee(40, "Tony", 60000)
        };

        System.out.println(" Before sorting => " + Arrays.toString(employees));
        Arrays.sort(employees, (o1, o2) -> o1.getSalary() - o2.getSalary());
        System.out.println(" After sorting => " + Arrays.toString(employees));
    }
}

Output:

 Before sorting => [Employee [id=10, name=Ramesh, salary=50000], Employee [id=20, name=John, salary=30000], Employee [id=30, name=tom, salary=40000], Employee [id=40, name=Tony, salary=60000]]
 After sorting => [Employee [id=20, name=John, salary=30000], Employee [id=30, name=tom, salary=40000], Employee [id=10, name=Ramesh, salary=50000], Employee [id=40, name=Tony, salary=60000]]

Java 8 Lambda - Sort an Array of Employee objects (by salary) in Descending Order

The following example sort an array of employee objects in descending order:

package com.java.array.tutorial.sorting;

import java.util.Arrays;

public class SortArray {
    public static void main(String[] args) {

        // sort Array of employee objects using Comparator interface

        Employee[] employees = {
            new Employee(10, "Ramesh", 50000),
            new Employee(20, "John", 30000),
            new Employee(30, "tom", 40000),
            new Employee(40, "Tony", 60000)
        };

        System.out.println(" Before sorting => " + Arrays.toString(employees));
        Arrays.sort(employees, (o1, o2) -> o2.getSalary() - o1.getSalary());
        System.out.println(" After sorting => " + Arrays.toString(employees));
    }
}

Output:

 Before sorting => [Employee [id=10, name=Ramesh, salary=50000], Employee [id=20, name=John, salary=30000], Employee [id=30, name=tom, salary=40000], Employee [id=40, name=Tony, salary=60000]]
 After sorting => [Employee [id=40, name=Tony, salary=60000], Employee [id=10, name=Ramesh, salary=50000], Employee [id=30, name=tom, salary=40000], Employee [id=20, name=John, salary=30000]]

Also, check out Java Sort Array Objects using Comparable Interface.

Check out Comparator example at https://www.javaguides.net/2018/12/java-comparator-interface-example.html

Learn Java Array at https://www.javaguides.net/2020/04/java-array-tutorial-for-beginners.html.