My feature file contains a feature that needs to be reused by each and every step definition file again & again. How to manage the code

My feature is :-
"User is on home Page".

The above feature / scenario contains a code that needs to be reused again & again. In my code base , for every feature file i have written separate step definition. 

*My first step definition file* :-

```
@Given ("^user is on  HomePage$")
    public void user_homePage()
    {
        configFileReader =new ConfigFileReader();
        System.setProperty("webdriver.chrome.driver","D:\\chromedriver.exe");
        driver=new ChromeDriver();
        driver.get("https://parabank.parasoft.com/parabank/index.htm");
        driver.manage().window().maximize();
    }

```

Now the same feature needs to be used in another step definition file. i.e 
here below 

Before user clicks on 'Register' link , it should verify that user is on homePage. The description of 'User is on home page' is defined in first step definition file . 

Now how to manage the code here :-

*My Second Step definition file here below*:-

import StepFiles.ParaBank\_TC\_01\_Step; [ I have even imported first step definition file , so that feature "User is on home page" could be executed. ]

```
public class ParaBank_TC_02_Step  {

    public  WebDriver driver;
    ConfigFileReader configFileReader;

      @When ("^user clicks on register link$")
        public void click_register() throws InterruptedException
        {

             Thread.sleep(3000);     
             WebElement register_link= driver.findElement(By.xpath("//a[contains(text(),'Register')]"));
             register_link.click();
        }

```

Actual Result :- 
1. When i write all the step definition for 2 features files in one file , then it executes perfectly fine , because feature 'User is on home page' is defined in one same file.

2. As i write separate step definition for feature 2 in another java file. It shows me "Null pointer exception" error because on feature "User is on home page" > driver is initialised in 1 step def file . It isn't executing for second step definition file.

Please help me out in understanding the root cause of this issue & provide the best possible solution.