Comparator interface to sort java object based on it's parameter.

Sort list of Employee object based on it's name parameter.

1.Bean class:

package com.collection.javacodepractices;

public class Employee {

      private int rollNo;

      private String name;

      public int getRollNo() {

            return rollNo;

      }

      public void setRollNo(int rollNo) {

            this.rollNo = rollNo;

      }

      public String getName() {

            return name;

      }

      public void setName(String name) {

            this.name = name;

      }

      @Override

      public String toString() {

            return "Employee [rollNo=" + rollNo + ", name=" + name + "]";

      }

}

2.Comparable class:

package com.collection.javacodepractices;

import java.util.Comparator;

public class EmployeeComparable implements Comparator<Employee>{

      @Override

      public int compare(Employee empOne, Employee empTwo) {

            return (empOne.getName().compareToIgnoreCase(empTwo.getName())<0?-1:                                                   (empOne.getName().equalsIgnoreCase(empTwo.getName())?0:1));

      }

}

3.Client class:

package com.collection.javacodepractices;

import java.util.ArrayList;

import java.util.Collections;

import java.util.List;

public class Client {

      public static void main(String args[]) {

            List<Employee> empList = new ArrayList<Employee>();

            // 1. employee setting.

            Employee emp1 = new Employee();

            emp1.setRollNo(1);

            emp1.setName("Bijoy");

            // 2. employee setting.

            Employee emp2 = new Employee();

            emp2.setRollNo(2);

            emp2.setName("Bappa");

            // 3. employee setting.

            Employee emp3 = new Employee();

            emp3.setRollNo(3);

            emp3.setName("Chintu");

            // 4. employee setting.

            Employee emp4 = new Employee();

            emp4.setRollNo(4);

            emp4.setName("Rahul");

            // 5. employee setting.

            Employee emp5 = new Employee();

            emp5.setRollNo(5);

            emp5.setName("Ajoy");

           

            //Add employee object to list.

            empList.add(emp1);

            empList.add(emp2);

            empList.add(emp3);

            empList.add(emp4);

            empList.add(emp5);

           

            //sorting employee based on name using comparator interface.

            Collections.sort(empList, new EmployeeComparable());

           

            //Print Employee object.

            for(Employee emp:empList){

                  System.out.println(emp.toString());

            }

      }

}

OUTPUT:

Employee [rollNo=5, name=Ajoy]

Employee [rollNo=2, name=Bappa]

Employee [rollNo=1, name=Bijoy]

Employee [rollNo=3, name=Chintu]

Employee [rollNo=4, name=Rahul]