Complete End to End Java Tutorial with Singleton Object & Employee, Crunchify Java POJO & Detailed TestCase

In this Java Tutorial we will go over all detailed steps required for you to use Singleton pattern in your Enterprise Project. We use Singleton object to push required data at runtime and we use the same Singleton object to retrieve data at runtime. You could access Singleton object from anywhere. If you want to learn more about Singleton Pattern the follow this Singleton tutorial.

Let’s get started on steps.

Step 1: Create simple Crunchify Object POJO: CrunchifyObject.java

Step 2: Create all setters and getters.

Step 3: Create Singleton Class: CrunchifySingleton.java

Step 4: Write all utility methods into Singleton class

Step 5: Finally create Test Class: CrunchifyObjectTest.java

package crunchify.com.tutorial;

import java.util.List;

/**
 * @author Crunchify.com 
 * This is simple CrunchifyObject POJO contains another class "Employee" as a field
 */

public class CrunchifyObject {
	public String name;
	public String address;
	public List<Employee> employees;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getAddress() {
		return address;
	}

	public void setAddress(String address) {
		this.address = address;
	}

	public List<Employee> getEmployees() {
		return employees;
	}

	public void setEmployees(List<Employee> employees) {
		this.employees = employees;
	}

	// Class Employee
	public class Employee {
		public String firstName;
		public String lastName;
		public int phoneNumber;

		public String getFirstName() {
			return firstName;
		}

		public void setFirstName(String firstName) {
			this.firstName = firstName;
		}

		public String getLastName() {
			return lastName;
		}

		public void setLastName(String lastName) {
			this.lastName = lastName;
		}

		public int getPhoneNumber() {
			return phoneNumber;
		}

		public void setPhoneNumber(int phoneNumber) {
			this.phoneNumber = phoneNumber;
		}
	}
}

package crunchify.com.tutorial;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.json.JSONArray;
import org.json.JSONObject;

import crunchify.com.tutorial.CrunchifyObject.Employee;

/**
 * @author Crunchify.com 
 * This is Singleton class used to access from any where from your project. Here we are using it
 *         from CrunchifyObjectTest.java
 *
 */
public class CrunchifySingleton {

	private List<Employee> employees = new ArrayList<Employee>();
	private static CrunchifySingleton singletonInstance = null;
	private CrunchifyObject crunchify = new CrunchifyObject();

	public static CrunchifySingleton getCrunchifySingletonInstance() {
		if (singletonInstance == null) {
			singletonInstance = new CrunchifySingleton();
		}
		return singletonInstance;
	}

	public void addEmployee(Employee employee) {
		synchronized (employees) {
			employees.add(employee);
		}
	}

	public List<Employee> getEmployee() {
		return employees;
	}

	public void addCrunchify(CrunchifyObject crunchify) {
		synchronized (crunchify) {
			this.crunchify = crunchify;
		}
	}

	public String getCrunchifyObject() {
		JSONObject obj = new JSONObject();
		obj.put("name", crunchify.getName());
		obj.put("address", crunchify.getAddress());

		JSONArray employeeJson = new JSONArray();
		for (Employee emp : employees) {

			Map<String, String> employeeData = new HashMap<String, String>();
			employeeData.put("firstName", emp.getFirstName());
			employeeData.put("lastName", emp.getLastName());
			employeeData.put("phoneNumber", emp.getPhoneNumber() + "");

			employeeJson.put(employeeData);
		}
		obj.put("employees", employeeJson);
		return obj.toString();
	}
}

package crunchify.com.tutorial;

import crunchify.com.tutorial.CrunchifyObject.Employee;

/**
 * @author Crunchify.com 
 * This is test class used to create all required objects and use Singleton object to push and
 *         retrieve value at runtime. You could use the same singleton object from anywhere in your enterprise project
 */

public class CrunchifyObjectTest {

	static CrunchifySingleton instance = CrunchifySingleton.getCrunchifySingletonInstance();

	public static void main(String[] args) {
		populateAndSaveDataFromSingletonObject();
		retrieveDataFromSingletonObject();
	}

	private static void retrieveDataFromSingletonObject() {
		String result = instance.getCrunchifyObject();
		System.out.println(result);
	}

	private static void populateAndSaveDataFromSingletonObject() {

		// Create CrunchifyObject
		CrunchifyObject crunchifyObj = new CrunchifyObject();
		crunchifyObj.setName("Crunchify.com");
		crunchifyObj.setAddress("NYC - US");

		// Create Employee1
		Employee emp1 = crunchifyObj.new Employee();
		emp1.setFirstName("Mike");
		emp1.setLastName("Rose");
		emp1.setPhoneNumber(1222222222);

		// Create Employee2
		Employee emp2 = crunchifyObj.new Employee();
		emp2.setFirstName("Arpit");
		emp2.setLastName("Shah");
		emp2.setPhoneNumber(1333333333);

		// Create Employee3
		Employee emp3 = crunchifyObj.new Employee();
		emp3.setFirstName("Dexter");
		emp3.setLastName("My");
		emp3.setPhoneNumber(1444444444);

		// Add all Employee Object to CrunchifySingleton object
		instance.addEmployee(emp1);
		instance.addEmployee(emp2);
		instance.addEmployee(emp3);

		// Add Employees to CrunchifyObject
		crunchifyObj.setEmployees(instance.getEmployee());

		// Now finally add CrunchifyObject to same CrunchifySingleton object which will use to retrieve all data
		instance.addCrunchify(crunchifyObj);
	}

}

Result:

{
    "address": "NYC - US",
    "name": "Crunchify.com",
    "employees": [
        {
            "lastName": "Rose",
            "phoneNumber": "1222222222",
            "firstName": "Mike"
        },
        {
            "lastName": "Shah",
            "phoneNumber": "1333333333",
            "firstName": "Arpit"
        },
        {
            "lastName": "My",
            "phoneNumber": "1444444444",
            "firstName": "Dexter"
        }
    ]
}

The post Complete End to End Java Tutorial with Singleton Object & Employee, Crunchify Java POJO & Detailed TestCase appeared first on Crunchify.
Author: Arpit Shah