getting an exception while accessing method from another class

Question

while accessing method from another class, i am getting NullPointer exception in selenium.

The method is actually working when try to run it individually but showing exception while accessing the method. i have tried with implicit wait and explicit wait and thread sleep in main class before calling the method but the result is same

//method class

WebDriver driver ;
public void bankId() throws InterruptedException {
Scanner sc = new Scanner(System.in);
        
        System.out.println("Enter the id u want to login");
        
        int id = sc.nextInt();
    //  driver.findElement(By.id("TradeId")).click();
        
        if (id == 1){
            System.out.println("welcome to Canara Bank");
            driver.manage().timeouts().implicitlyWait(10,TimeUnit.SECONDS);
            Select s = new Select(driver.findElement(By.id("TradeId")));
            s.selectByValue("1");
        }
        
        else if(id == 2){
            System.out.println("welcome to Allahabad Bank");
            driver.manage().timeouts().implicitlyWait(10,TimeUnit.SECONDS);
            Select s = new Select(driver.findElement(By.id("TradeId")));
            s.selectByValue("2");
        }
        
        else if(id == 3){
            System.out.println("welcome to Corporation Bank");
            driver.manage().timeouts().implicitlyWait(10,TimeUnit.SECONDS);
            Select s = new Select(driver.findElement(By.id("TradeId")));
            s.selectByValue("3");
        }
        
        else if(id == 4){
            System.out.println("CUB Bank");
            Thread.sleep(2000);
            Select s = new Select(driver.findElement(By.id("TradeId")));
            s.selectByValue("4");
        }
        
        else {
            System.out.println("bank id incorrect, please try again");
        }
        
        driver.manage().timeouts().implicitlyWait(10,TimeUnit.SECONDS);

//main class

public static void main(String[] args) throws InterruptedException {
        // TODO Auto-generated method stub

        WebDriver driver;
        
        System.setProperty("webdriver.chrome.driver", "E:\\Automation\\jarfiles2\\chromedriver_win32_new\\chromedriver.exe");
        driver = new ChromeDriver();
        
        driver.manage().window().maximize();
        driver.get("localhost/Role/AdminIntermediary");
        
        
    //username 
        driver.manage().timeouts().implicitlyWait(10,TimeUnit.SECONDS);
        driver.findElement(By.name("UserName")).sendKeys("admin");
        
    //pass
        driver.manage().timeouts().implicitlyWait(10,TimeUnit.SECONDS);
        driver.findElement(By.name("Password")).sendKeys("adminadmin");
        
    //login
        driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);
        driver.findElement(By.xpath("//input[@type='submit']")).click();
        
        Thread.sleep(5000);
        driver.navigate().to("localhost/settings");
        
        driver.manage().timeouts().implicitlyWait(20, TimeUnit.SECONDS);
        
    //getting the list of banks
        List<WebElement> options = driver.findElements(By.id("TradeId"));
        for (int i=0;i<options.size();i++){
            String menu = options.get(i).getText();
            
            System.out.println(menu);
        }
    
    //Selecting particular bank
        driver.manage().timeouts().implicitlyWait(10,TimeUnit.SECONDS);
        
        GSTlogin gl = new GSTlogin();
        gl.bankId();
        

//stack trace

Exception in thread "main" java.lang.NullPointerException
    at GSTlogin.bankId(GSTlogin.java:76)
    at bank.main(bank.java:58)