Question

Here is my code:

public static String currentStudent = "";


public void login() {
  boolean studentLoggedOn = false;
  Student student = new Student();
  PC_Dialog dialog = new PC_Dialog("Enter Login Information", "Student ID, Password-", "OK");
  dialog.choice();

  String studentID = dialog.getField(1);
  String password = dialog.getField(2);

  student = (Student) projectSystem.studentFile.retrieve(studentID);

  if (studentID != null) {
     if (password.equals(student.password)) {
        currentStudent = studentID;
        studentLoggedOn = true;
        studentRun();
     }
  }

  if (!studentLoggedOn) {
     JOptionPane.showMessageDialog(null, "Either the user name or the password were incorrect");
     login();

}
   }

After all of that, the “currentStudent = studentID;” doesn’t seem to have any effect on the currentStudent String?

Answer 1

Your question is incomplete, but if I had to guess, I’d say you have a reference to currentStudent somewhere else in your code. Since strings are not mutable and the assignment operator also does not mutate objects, this reference would not change.

For example:

String one = "some string";
String two = one;
one = "another";
System.out.println(one);
System.out.println(two);

Will output

another
some string

Try reading up on Java references and string assignment.

Per the question author’s request here’s an example that accomplishes what I think he wants.

public class Session {
    private String currentUserId = null;
    public void setCurrentUserId( String id ) {
        currentUserId = id;
    }
    public String getCurrentUserId() {
        return currentUserId;
    }
    // Other session related information
    //... 
}

And use the Session class as follows.

public class MyApp  {
    private Session currentSession;
    public MyApp() {
        currentSession = new Session();
    }
    public void login() {
        //...
        if ( studentID != null ) {
            if ( password.equals(student.password) ) {
                currentSession.setCurrentUserId(studentID);
                //...
            }
        }
        //...
    }
    public void someOtherMethod() {
        System.out.println(currentSession.getCurrentUserId());
    }
}