import java.util.Objects;

class Employee implements Comparable<Employee> {
    private int id;
    private String name;
    private double salary;
    private LocalDate joiningDate;

    public Employee(int id, String name, double salary, LocalDate joiningDate) {
        this.id = id;
        this.name = name;
        this.salary = salary;
        this.joiningDate = joiningDate;
    }

    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 double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public LocalDate getJoiningDate() {
        return joiningDate;
    }

    public void setJoiningDate(LocalDate joiningDate) {
        this.joiningDate = joiningDate;
    }

    // compare two employees based on their ID
    @Override
    public int compareTo(Employee another) {
        return this.getID() - another.getID();
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass) {
            return false;
        }
        Employee employee = (Employee) o;
        return id = employee.id;
    }

    @Override
    public int hashCode() {
        return Objects.hash(id);
    }

    @Override
    public String toString() {
        return "Employee{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", salary=" + salary +
                ", joiningDate=" + joiningDate +
                '}';
    }
}

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

public class ComparableExample {
    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)));

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

        // This will use the `compareTo()` method of the `Employee` class to compare two employees and sort them.
        Collections.sort(employees);

        System.out.println("\nEmployees (After Sorting) : " + employees);
    }
}

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
        Comparator<Employee> employeeNameComparator = new Comparator<Employee>() {
            @Override
            public int compare(Employee e1, Employee e2) {
                return e1.getName().compareTo(e2.getName());
            }
        };

        //employeeNameComparator = (e1, e2) -> e1.getName().compareTo(e2.getName());
        Collections.sort(employees, employeeNameComparator);
        System.out.println("\nEmployees (Sorted by Name) : " + employees);

        // Sort employees by Salary
        Comparator<Employee> employeeSalaryComparator = new Comparator<Employee>() {
            @Override
            public int compare(Employee e1, Employee e2) {
                if(e1.getSalary() < e2.getSalary()) {
                    return -1;
                } else if (e1.getSalary() > e2.getSalary()) {
                    return 1;
                } else {
                    return 0;
                }
            }
        };

        Collections.sort(employees, employeeSalaryComparator);
        System.out.println("\nEmployees (Sorted by Salary) : " + employees);

        // Sort employees by JoiningDate
        Comparator<Employee> employeeJoiningDateComparator = new Comparator<Employee>() {
            @Override
            public int compare(Employee e1, Employee e2) {
                return e1.getJoiningDate().compareTo(e2.getJoiningDate());
            }
        };

        Collections.sort(employees, employeeJoiningDateComparator);
        System.out.println("\nEmployees (Sorted by JoiningDate) : " + employees);
    }
}

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);
    }