How to convert java object to json string using Gson APIs?

<project xmlns="http://maven.apache.org/POM/4.0.0" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
    					http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>gson_exmp</groupId>
  <artifactId>gson_exmp</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <dependencies>
  	<dependency>
  		<groupId>com.google.code.gson</groupId>
  		<artifactId>gson</artifactId>
  		<version>2.3.1</version>
  	</dependency>
  </dependencies>
</project>

package com.java2novice.json.gson;

public class Employee {

	private int empId;
	private String name;
	private String designation;
	private String department;
	private int salary;
	
	public int getEmpId() {
		return empId;
	}
	public void setEmpId(int empId) {
		this.empId = empId;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getDesignation() {
		return designation;
	}
	public void setDesignation(String designation) {
		this.designation = designation;
	}
	public String getDepartment() {
		return department;
	}
	public void setDepartment(String department) {
		this.department = department;
	}
	public int getSalary() {
		return salary;
	}
	public void setSalary(int salary) {
		this.salary = salary;
	}
}

package com.java2novice.json.gson;

import com.google.gson.Gson;

public class ObjectToJsonEx {

	public static void main(String a[]){
		
		Employee emp = new Employee();
		emp.setEmpId(1016);
		emp.setName("Nataraj G");
		emp.setSalary(20000);
		emp.setDesignation("Manager");
		emp.setDepartment("Accounts");
		
		Gson gsonObj = new Gson();
		// converts object to json string
		String jsonStr = gsonObj.toJson(emp);
		System.out.println(jsonStr);
	}
}

{"empId":1016,"name":"Nataraj G","designation":"Manager","department":"Accounts","salary":20000}