Comparable and Comparator

import java.util.Comparator;

public class Employee implements Comparable<Employee> {

    private int id;

    private String name;

    private int age;

    private long salary;

    public int getId() {

        return id;

    }

    public String getName() {

        return name;

    }

    public int getAge() {

        return age;

    }

    public long getSalary() {

        return salary;

    }

    public Employee(int id, String name, int age, int salary) {

        this.id = id;

        this.name = name;

        this.age = age;

        this.salary = salary;

    }

    @Override

    public int compareTo(Employee emp) {

        //let's sort the employee based on id in ascending order

        //returns a negative integer, zero, or a positive integer as this employee id

        //is less than, equal to, or greater than the specified object.

        return (this.id - emp.id);

    }

    @Override

    //this is required to print the user friendly information about the Employee

    public String toString() {

        return "[id=" + this.id + ", name=" + this.name + ", age=" + this.age + ", salary=" +

                this.salary + "]";

    }

}

/**

     * Comparator to sort employees list or array in order of Salary

     */

    public static Comparator<Employee> SalaryComparator = new Comparator<Employee>() {

        @Override

        public int compare(Employee e1, Employee e2) {

            return (int) (e1.getSalary() - e2.getSalary());

        }

    };

    /**

     * Comparator to sort employees list or array in order of Age

     */

    public static Comparator<Employee> AgeComparator = new Comparator<Employee>() {

        @Override

        public int compare(Employee e1, Employee e2) {

            return e1.getAge() - e2.getAge();

        }

    };

    /**

     * Comparator to sort employees list or array in order of Name

     */

    public static Comparator<Employee> NameComparator = new Comparator<Employee>() {

        @Override

        public int compare(Employee e1, Employee e2) {

            return e1.getName().compareTo(e2.getName());

        }

    };

.//sort employees array using Comparator by Salary

Arrays.sort(empArr, Employee.SalaryComparator);

System.out.println("Employees list sorted by Salary:\n"+Arrays.toString(empArr));

//sort employees array using Comparator by Age

Arrays.sort(empArr, Employee.AgeComparator);

System.out.println("Employees list sorted by Age:\n"+Arrays.toString(empArr));

//sort employees array using Comparator by Name

Arrays.sort(empArr, Employee.NameComparator);

System.out.println("Employees list sorted by Name:\n"+Arrays.toString(empArr))

import java.util.Comparator;

public class EmployeeComparatorByIdAndName implements Comparator {

    @Override

    public int compare(Employee o1, Employee o2) {

        int flag = o1.getId() - o2.getId();

        if(flag==0) flag = o1.getName().compareTo(o2.getName());

        return flag;

    }

}

import java.util.Arrays;

public class JavaObjectSorting {

    /**

     * This class shows how to sort custom objects array/list

     * implementing Comparable and Comparator interfaces

     * @param args

     */

    public static void main(String[] args) {

        //sorting custom object array

        Employee[] empArr = new Employee[4];

        empArr[0] = new Employee(10, "Mikey", 25, 10000);

        empArr[1] = new Employee(20, "Arun", 29, 20000);

        empArr[2] = new Employee(5, "Lisa", 35, 5000);

        empArr[3] = new Employee(1, "Pankaj", 32, 50000);

        

        //sorting employees array using Comparable interface implementation

        Arrays.sort(empArr);

        System.out.println("Default Sorting of Employees list:\n"+Arrays.toString(empArr));

        

        //sort employees array using Comparator by Salary

        Arrays.sort(empArr, Employee.SalaryComparator);

        System.out.println("Employees list sorted by Salary:\n"+Arrays.toString(empArr));

        

        //sort employees array using Comparator by Age

        Arrays.sort(empArr, Employee.AgeComparator);

        System.out.println("Employees list sorted by Age:\n"+Arrays.toString(empArr));

        

        //sort employees array using Comparator by Name

        Arrays.sort(empArr, Employee.NameComparator);

        System.out.println("Employees list sorted by Name:\n"+Arrays.toString(empArr));

        

        //Employees list sorted by ID and then name using Comparator class

        empArr[0] = new Employee(1, "Mikey", 25, 10000);

        Arrays.sort(empArr, new EmployeeComparatorByIdAndName());

        System.out.println("Employees list sorted by ID and Name:\n"+Arrays.toString(empArr));

    }

}