Java Program to Group the Employees by City

1. Introduction

In this tutorial, we'll develop a Java program to group employees by their city. This technique is widely useful in organizing and analyzing employee data by geographic distribution, which can assist in various strategic decisions.

2. Program Steps

1. Define the Employee class with appropriate attributes such as id, name, age, salary, gender, deptName, city, and constructor.

2. Create a GroupEmployees class that will contain the main method.

3. In the main method, instantiate a list of Employee objects and group them by city.

4. Display the results of the grouping.

3. Code Program

Creating Employee Class

Let's create an Employee class and add the following code to it:

// File: Employee.java
public class Employee {
    private int id;
    private String name;
    private int age;
    long salary;
    private String gender;
    private String deptName;
    private String city;

    public Employee(int id, String name, int age, long salary, String gender, String deptName, String city) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.salary = salary;
        this.gender = gender;
        this.deptName = deptName;
        this.city = city;
    }

    public String getCity() {
        return city;
    }

    @Override
    public String toString() {
        return String.format("%d %s %d %d %s %s %s", id, name, age, salary, gender, deptName, city);
    }
}

Create GroupEmployees Class and Write Logic

Let's create a GroupEmployees class and add the following code to it:

// File: GroupEmployees.java
import java.util.*;
import java.util.stream.Collectors;

public class GroupEmployees {
    public static void main(String[] args) {
        List<Employee> employees = Arrays.asList(
            new Employee(1, "Aditi", 30, 100000, "F", "HR", "Mumbai"),
            new Employee(2, "Rahul", 34, 130000, "M", "Tech", "Bangalore"),
            new Employee(3, "Vishal", 28, 110000, "M", "Tech", "Mumbai"),
            new Employee(4, "Lakshmi", 45, 150000, "F", "HR", "Bangalore")
        );

        Map<String, List<Employee>> groupedByCity = employees.stream()
            .collect(Collectors.groupingBy(Employee::getCity));

        groupedByCity.forEach((city, empList) -> {
            System.out.println("City: " + city);
            empList.forEach(System.out::println);
        });
    }
}

Output:

City: Mumbai
1 Aditi 30 100000 F HR Mumbai
3 Vishal 28 110000 M Tech Mumbai
City: Bangalore
2 Rahul 34 130000 M Tech Bangalore
4 Lakshmi 45 150000 F HR Bangalore

Explanation:

1. The Employee class is defined with private fields and a constructor to initialize the object.

2. The GroupEmployees class contains the main method where the list of employees is created.

3. Employees are grouped by city using the collectors.groupingBy method.

4. Each city and its corresponding list of employees are printed on the console.