Sort User-Defined Objects using Comparator Interface

java.uti.Collections Examples

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• Sort User-Defined Objects using Comparator Interface
• Sort User-Defined Objects in Descending Order in Java
• Sort User-Defined Objects in Ascending Order in Java
• Sort Integer in Descending Order in Java Example
• Sort Integer in Ascending Order in Java Example
• Sort String in Descending Order in Java
• Sort String in Ascending Order in Java

import java.time.LocalDate;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class ComparatorExample {
    public static void main(String[] args) {
        List<Employee> employees = new ArrayList<>();

        employees.add(new Employee(1010, "Rajeev", 100000.00, LocalDate.of(2010, 7, 10)));
        employees.add(new Employee(1004, "Chris", 95000.50, LocalDate.of(2017, 3, 19)));
        employees.add(new Employee(1015, "David", 134000.00, LocalDate.of(2017, 9, 28)));
        employees.add(new Employee(1009, "Steve", 100000.00, LocalDate.of(2016, 5, 18)));

        System.out.println("Employees : " + employees);

        // Sort employees by Name
        Collections.sort(employees, Comparator.comparing(Employee::getName));
        System.out.println("\nEmployees (Sorted by Name) : " + employees);

        // Sort employees by Salary
        Collections.sort(employees, Comparator.comparingDouble(Employee::getSalary));
        System.out.println("\nEmployees (Sorted by Salary) : " + employees);

        // Sort employees by JoiningDate
        Collections.sort(employees, Comparator.comparing(Employee::getJoiningDate));
        System.out.println("\nEmployees (Sorted by JoiningDate) : " + employees);

        // Sort employees by Name in descending order
        Collections.sort(employees, Comparator.comparing(Employee::getName).reversed());
        System.out.println("\nEmployees (Sorted by Name in descending order) : " + employees);

        // Chaining multiple Comparators
        // Sort by Salary. If Salary is same then sort by Name
        Collections.sort(employees, Comparator.comparingDouble(Employee::getSalary)
                   .thenComparing(Employee::getName));
        System.out.println("\nEmployees (Sorted by Salary and Name) : " + employees);
    }
}

Output:

Employees : [Employee{id=1010, name='Rajeev', salary=100000.0, joiningDate=2010-07-10}, 
Employee{id=1004, name='Chris', salary=95000.5, joiningDate=2017-03-19}, 
Employee{id=1015, name='David', salary=134000.0, joiningDate=2017-09-28},
 Employee{id=1009, name='Steve', salary=100000.0, joiningDate=2016-05-18}]

Employees (Sorted by Name) : 
[Employee{id=1004, name='Chris', salary=95000.5, joiningDate=2017-03-19}, 
Employee{id=1015, name='David', salary=134000.0, joiningDate=2017-09-28},
 Employee{id=1010, name='Rajeev', salary=100000.0, joiningDate=2010-07-10}, 
Employee{id=1009, name='Steve', salary=100000.0, joiningDate=2016-05-18}]

Employees (Sorted by Salary) : 
[Employee{id=1004, name='Chris', salary=95000.5, joiningDate=2017-03-19},
 Employee{id=1010, name='Rajeev', salary=100000.0, joiningDate=2010-07-10},
 Employee{id=1009, name='Steve', salary=100000.0, joiningDate=2016-05-18}, 
Employee{id=1015, name='David', salary=134000.0, joiningDate=2017-09-28}]

Employees (Sorted by JoiningDate) : 
[Employee{id=1010, name='Rajeev', salary=100000.0, joiningDate=2010-07-10},
 Employee{id=1009, name='Steve', salary=100000.0, joiningDate=2016-05-18},
 Employee{id=1004, name='Chris', salary=95000.5, joiningDate=2017-03-19}, 
Employee{id=1015, name='David', salary=134000.0, joiningDate=2017-09-28}]

Employees (Sorted by Name in descending order) : 
[Employee{id=1009, name='Steve', salary=100000.0, joiningDate=2016-05-18}, 
Employee{id=1010, name='Rajeev', salary=100000.0, joiningDate=2010-07-10},
 Employee{id=1015, name='David', salary=134000.0, joiningDate=2017-09-28}, 
Employee{id=1004, name='Chris', salary=95000.5, joiningDate=2017-03-19}]

Employees (Sorted by Salary and Name) :
 [Employee{id=1004, name='Chris', salary=95000.5, joiningDate=2017-03-19},
 Employee{id=1010, name='Rajeev', salary=100000.0, joiningDate=2010-07-10},
 Employee{id=1009, name='Steve', salary=100000.0, joiningDate=2016-05-18}, 
Employee{id=1015, name='David', salary=134000.0, joiningDate=2017-09-28}]