String length problem

[Planet_x]

I am working with a basic Student class that has variables for names, address, assignment marks and midterm/final test marks. I'm having trouble with string length i need to check if the string length of each variable is equal to 0. If it is im supposed to have a dialogue box display an error and set the value to unknown.

Here is my code so far, it compiles up until the string length part which i am having issues with, any help appreciated.


public class Student
{
// Declare Variables - set fields for student class
private String FirstName;
private String LastName;
private char Initial;
private String StreetAddress;
private String City;
private String Postal;
private String Phonenumber;
private float Assignmentmark1;
private float Assignmentmark2;
private float Assignmentmark3;
private float Assignmentmark4;
private float Midtermmark;
private float Finalmark;



// Constructor to initialize all variables above - Default Constructor with no parameters
public Student()
{
FirstName = "";
LastName = "";
Initial = 'A';
StreetAddress = "";
City = "";
Postal = "";
Phonenumber = "";
Assignmentmark1 = 0;
Assignmentmark2 = 0;
Assignmentmark3 = 0;
Assignmentmark4 = 0;
Midtermmark = 0;
Finalmark = 0;

}

// Constructor with paramaters - except for the 6 marks
public Student(String studentFirstname, String studentLastname, char studentInitial, String studentStreetAddress, String studentCity, String studentPostal, String studentPhonenumber)
{
FirstName = studentFirstname;
LastName = studentLastname;
Initial = studentInitial;
StreetAddress = studentStreetAddress;
City = studentCity;
Postal = studentPostal;
Phonenumber = studentPhonenumber;

}

// Mutator method to set the First Name
public void setFirstname(String studentFirstname)
{
FirstName = studentFirstname;
if(String studentFirstname.length = 0)
{
System.out.println("Invalid Name");
studentFirstname = "unknown";
}


}

</br>

[forty2]

public class Test
{
private String first_name;

public void setFirstName(String first_name)
{
this.first_name = first_name;

if(first_name.length() == 0)
{
System.out.println("Invalid Name");
first_name = "unknown";
}
}

public static void main(String[] args)
{
Test a = new Test();
a.setFirstName("");

}
}

This is not JavaScript :) In Java length is method :)

[Khalid Ali]

its wrong comparison

if(first_name.length() == 0 || first_name.equals("")){

}

try the above