Trying to use a user-entered string from one class into a different class in Java

Question

I'm trying to create this payroll system which has a login class and a salary-calculator class. I'm trying to use the username string entered by the user in the login class in the salary calculator class to determine the basic salary, but the username string is treated as null in the salary-calculator class hence I'm getting a lot of errors. I'm quite new to java programming so I would highly appreciate your help. Here is my code.

  public class loginpage {
   Scanner x;   // declares scanner
 static String name;
  static String username; 
       public void username(){
       String filepath = "/home/ogweno/NetBeansProjects/Payroll System/src/payroll/system/employees.txt"; // Declaring the filepath
      // Declaring a string for the username
       String password;  // Declaring a string for the password
       String username;
     
      username = JOptionPane.showInputDialog("Please enter your username: ", "username");
     
       
     
      password=JOptionPane.showInputDialog("Please enter your Password: ");
       VerifyLoginA(username, password, filepath);
       }
       
public void VerifyLoginA(String username, String password, String filepath) {
       boolean flag = false;     // boolean variable set to false for later use
       String tempUsername = "";  // variable used for extracting the username from txt file and storing in this
       String tempPassword = "";  // variable used for extracting the password from txt file and storing in this
       try {
             x = new Scanner(new File(filepath)); //opens the file "/home/ogweno/Students.txt"
             x.useDelimiter("[,\n]");    // use of delimiter to specify the seperation of username & password by ","
            
             boolean passed = false;     // boolean variable set to false and later use
           while (x.hasNext()&& !flag){  // use of while to check if the file has any contents 
               
               tempUsername = x.next(); // extracts the username and stores it 
               tempPassword = x.next();// extracts the password and stores it 
               if (tempUsername.trim().equals(username.trim()) && tempPassword.trim().equals(password.trim())) {
                   passed = true; // use of trim to remove any unwanted space in user input or in txt file
                   break; // boolean passedA becomes true if the username and passwords entered by user match the ones in file
               }
           }
           if(passed) { // if passedA is true then prints Welcome + the username
               // System.out.println("Welcome " + username);
               //System.out.println(""); // space
               JOptionPane.showMessageDialog(null,"Welcome " + username);
                 boolean check = true;
                 
                 setName(username);
               
           }
          
           else { // if passedA is false then prints a error message
              // System.out.println("********WARNING**Incorrect Username or Password*********");
                 JOptionPane.showMessageDialog(null,"********WARNING**Incorrect Username or Password*********");
                 boolean check = false;
               System.exit(0); // Terminates program if username and/or password is incorrect
           }
          
           
           
       }
       catch (FileNotFoundException e){ // prints error if there is an error in opening the file
           System.out.println("Error");
       }
     
   }

   public static void setName(String usernamename) {
       name=username;
      //To change body of generated methods, choose Tools | Templates.
   }
   public static String getName(){
       return name;
   }
}

Here's the salary-calculator class

public class Salary_calculator extends loginpage {
    public void calculator(){
        int HS=10000;
        int TV=5000;
        int NSSF=2000;
        int NHIF=500;

loginpage login=new loginpage();

int grossPay=0;
String post="";
float netSalary;
if (name=="Jane"){
    grossPay=20000;
    post="Finance Officer";
}
else if (name=="Michael"){
    grossPay=30000;
    post="IT technician";
}
else if (name=="Josphine"){
    grossPay=40000;
    post="Marketing Officer";
}
else if (name=="Darshan"){
    grossPay=50000;
    post="Public Relations Officer";
}
else if (name=="Ketan"){
    grossPay=60000;
    post="Operations Manager";
}
 

int salary=grossPay + HS + TV -(NSSF+NHIF);
netSalary=(float) (0.7*salary);

JOptionPane.showMessageDialog(null, name + ": " + post + "\n" + "Your net salary is: " + netSalary + "\n");
    }
}

Answer 1

An example of accessing data in another class.

A minimal example class with one static and one non-static variable.

public class Payroll{
    public static String name1 = "static name1, same for all instances!";
    public String name2 = "name2, each instance has its own!";
}

Access the static name1 in Payroll from other classes:

String name = Payroll.name1;

Access the non-static name2 in Payroll from other classes:

Payroll payroll = new Payroll();
// Later, after the new instance has its data
String name = payroll.name2;

Remember, access to non-static variables requires that you have access to the instance. Every time you create a new instance with new it initially has no data or only standard data for you!

Edit: An example to demonstrate the interaction of two classes:

import java.util.*;
import javax.swing.*;

public class Payroll {
    static final List<Employee> employees = new ArrayList<>();

    public static void main(String[] args) {
        var payroll = new Payroll();

        var employee = payroll.login();
        JOptionPane.showMessageDialog(null, employee == null ? "Invalid Login!" : employee.getSalaryMessage());
    }

    public Payroll(){
        loadEmployees();
    }

    public Employee login(){
        String username = JOptionPane.showInputDialog("Please enter your Username:");
        String password = JOptionPane.showInputDialog("Please enter your Password:");
        for(var employee : employees) if(employee.isEmployee(username, password)) return employee;
        return null;
    }

    private void loadEmployees(){
        employees.add(new Employee("Jane", "jan", "xxx", 20000, "Finance Officer"));
        employees.add(new Employee("Michael", "mic", "yyy", 30000, "IT technician"));
        employees.add(new Employee("Josphine", "jos", "zzz", 40000, "Marketing Officer"));
        employees.add(new Employee("Darshan", "dar", "qqq", 50000, "Public Relations Officer"));
        employees.add(new Employee("Ketan", "ket", "ppp", 60000, "Operations Manager"));
    }
}

For completeness, the Employee class:

public class Employee {
    private String name;
    private String username;
    private String password;
    private double grossPay;
    private String post;

    public Employee(String name, String username, String password, double grossPay, String post){
        this.name = name;
        setUsername(username);
        setPassword(password);
        setGrossPay(grossPay);
        setPost(post);
    }

    public String getSalaryMessage(){
        return name + " (" + post + ") earns " + grossPay;
    }

    public boolean isEmployee(String username, String password){
        return this.username.equals(username) && this.password.equals(password);
    }

    public String getName(){ return name; }

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

    public String getUsername(){ return username; }

    public void setUsername(String username){ this.username = username; }

    public String getPassword(){ return password; }

    public void setPassword(String password){ this.password = password; }

    public double getGrossPay(){ return grossPay; }

    public void setGrossPay(double salary){ this.grossPay = salary; }

    public String getPost(){ return post; }

    public void setPost(String post){ this.post = post; }
}