Java dunce is back...still can't figure this out

[N. Gonzalez]

Still attempting to increment the student id when I print out the instances of the student data using toString() method.

In my Student class file, I have a a static class variable:

 private static int studentID = 1000 {/CODE]
an instance variable:
[CODE]private int studentid;

this is in the constructor:

studentID++;

a getter for the class variable:

static int getIDNum () {
            return (studentID);

a getter for the instance variable:

int getStudID () {
          return (studentid);

and the 'studentid' field in my toString() method.


Here's the test file; it compiles, but all the IDs are '0'.

public class StudentTest {
 
public static void main (String[] args) {
 
String course = Student.getCourse ();
String coursenumber = Student.getClassNum ();
String instructor = Student.getInstructor ();
System.out.println ("");
System.out.println(" Course: " + course + "\t Course Number: " + coursenumber + "\n Instructor: " + instructor + "\n");
 
Student [] studentarray = new Student [6];
studentarray [0] = new Student ("Mary","Smith","111 Smith Street","New York","NY",10001,"[e-mail]","212-555-1111",true);
studentarray [1] = new Student ("Bill","Brown","222 Brown Street","New York","NY",10002,"[e-mail]","212-555-2222",true);
studentarray [2] = new Student ("Jill","Jones","333 Jones Street","New York","NY",10003,"[e-mail]","212-555-3333",true);
studentarray [3] = new Student ("John","Martin","444 Martin Street","New York","NY",10004,"[e-mail]","212-555-4444",true);
studentarray [4] = new Student ("Bob","Wilson","555 Wilson Street","New York","NY",10005,"[e-mail]","212-555-5555",true);
studentarray [5] = new Student ("Betty","Boop","666 Boop Street","New York","NY",10006,"[e-mail]","212-555-6666",false);


System.out.println(" Full Class Roster:" + "\n");

for (int i=0; i<studentarray.length; i++){
int id = studentarray[i].getStudID ();
id++;
System.out.println(studentarray[i].toString() + "\n");
}

int enrolled = Student.getEnrollment ();
System.out.println("\n Number of students enrolled before prerequisite check: " + enrolled + "\n");
 
int idstatus = Student.getIDNum ();
System.out.println("\n Next Student ID# will be : " + idstatus);

}
}

[Madhumathy Viswanathan]

Remove the keyword static.When a variable is Static it maintains a common copy among all instances.Hence called class variable and not instance variable.

[Ulf Dittmer]

Makes sense that they would be 0, because you never set 'studentid', so they retain their implicit value (which is zero). Not seeing the full code, it would seem that 'studentid' is unnecessary, and you should just use 'studentID'. What purpose is served by having both of them? (As an aside, I would urge you not to have two fields with the same name that only differ in case; it's much too easy to make mistakes through typos).

[N. Gonzalez]

I was advised to have two variables, one of which should be static.

You really want this to be two variables. One to keep track of the current maximum assigned student id and one to keep track of the student id for that particular student. Tip: Think about which one of these needs to be static.

Here's my code for the Student class:

class Student{
//make all data private
/** 
 * create static class variables
 */
private static String classNumber = "P10.1234.01";
private static String className = "Advanced Topics in Poetry";
private static StringinstructorName = "Prof. Walt Whitman";
private static intenrollCount = 0;
private static intstudentID = 1000;
 
/**
 * create instance variables
 */

private Stringfirstname, lastname, streetaddress, city, state, emailaddress, telephone;
private intstudentid, zipcode;
private booleanprereq = true;

/**
 * Create a constructor for the class that takes student firstname and lastname;  
 * Constructor should generate a student id (start with 1000 and increment for each new student) 
 */
Student (String first, String last) {
firstname = first;
lastname = last;

studentID++;
 
enrollCount++;
}

/**
 * Create second constructor that takes all fields (firstname, lastname, address, city, etc.);  
 * Constructor should not take student id as an input parameter;
 * It should use the first constructor to initialize firstname and lastname
 */
Student (String first, String last, String street, String cty, String st, int zip, String email, String phone, boolean pre) {

this (first, last);

streetaddress = street;
city = cty;
state = st;
zipcode = zip;
emailaddress = email;
telephone = phone;
prereq = pre;
}

 /**
 * Getter methods for each class variable
 */
static String getClassNum () {
return (classNumber);
}
static String getCourse () {
return (className);
}
static String getInstructor () {
return (instructorName);
}
static int getEnrollment () {
return (enrollCount);
}
static int getIDNum () {
return (studentID);
}

 
/**
 * create getter and setter method for each instance variable
 */

int getStudID () {
return (studentid);
}
void setStudID (int studentid) {
this.studentid = studentid;
}
 
String getFirstName () {//accessors for first name field
return (firstname);
}
void  setFirstName (String firstname) {
this.firstname = firstname;
}
 
String getLastName () {//accessors for last name field
return (lastname);
}
void  setLastName (String lastname) {
this.lastname = lastname;
}
 
String getStreetAddress () {//accessors for street address field
return (streetaddress);
}
void  setStreetAddress (String streetaddress) {
this.streetaddress = streetaddress;
}
 
String getCity () {//accessors for city field
return (city);
}
void  setCity (String city) {
this.city = city;
}
 
String getState () {//accessors for state field
return (state);
}
void  setState (String state) {
this.state = state;
}
 
int getZipCode () {//accessors for zipcode field
return (zipcode);
}
void  setZipCode (int zipcode) {
this.zipcode = zipcode;
}
 
String getEmail () {//accessors for email field
return (emailaddress);
}
void  setEmail (String emailaddress) {
this.emailaddress = emailaddress;
}
 
String getTelephone () {//accessors for telephone field
return (telephone);
}
void  setTelephone (String telephone) {
this.telephone = telephone;
}
 
boolean getPreReq () {//accessors for prerequisite field
return (prereq);
}
void  setPreReq (boolean prereq) {
this.prereq = prereq;
}

/**
 * My own method
 */
public void prereqCheck () {
System.out.println ("Student has completed prerequisite course: Introduction to Poetry");
}

/**
 * Create a toString( ) string method for the class; it should output all data.
 */
 
public String toString () {
String studentprofile = "\t Student Name: " +  firstname + " " + lastname +
"\n \t Student ID Number: " + studentid +
"\n \t Address 1: " + streetaddress + 
"\n \t Address 2: " + city + ", " + state + " " + zipcode +
"\n \t Email Address: " + emailaddress + 
"\n \t Telephone: " + telephone;
return (studentprofile);
}
 
}
  

[Jaikiran Pai]

Add the following statement to your constructor:

studentid = studentID;

Your constructor would look like:

 Student (String first, String last) {
firstname = first;
lastname = last;
        studentID++; 
                        studentid = studentID;
        enrollCount++;
} 

[ July 25, 2005: Message edited by: jaikiran pai ]
[ July 25, 2005: Message edited by: jaikiran pai ]

[N. Gonzalez]

Thank you so much Jaikiran!

In the midst a number of making other changes, I recall doing this then removing it thinking it didn't work (so easy to make dumb mistakes when you're exhaused!)

It's a relief to know I wasn't far off. Thanks for peace of mind.

[Jaikiran Pai]

Nice to know, you got the expected output. Good day.