Why does this not work (teacher is stumped)

[valar3573]

A few of the methods arent written yet, but my problem is that when I choose to enter information, i get prompted for all the values, but when i open up the dat file, there is nothing there. The view contact method all does not print anything. I realize its a long program, but any help would be GREATLY appreciated. No one in my class has any clue, and im at my wits end.
thanks so much.


import java.io.*;
import java.util.*;
import static java.lang.System.*;


public class dossier
{
public static void main( String [] args ) throws IOException
{

Driver driver = new Driver();
driver.mainMenu();
}
}

class Contact implements Comparable
{ private String firstName;
private String lastName;
private String homePhone;
private String workPhone;
private String cellPhone;
private String email;
private String streetAddress;
private String city;
private String state;
private int zipCode;
private String country;



public int compareTo(Object o)
{
return 1;
}
public Contact()
{
firstName="";
lastName="";
homePhone="";
workPhone="";
cellPhone="";
email="";
streetAddress="";
city="";
state="";
zipCode=0;
country="";
}


public Contact(String firstName, String lastName, String homePhone,
String workPhone, String cellPhone, String email, String streetAddress,
String city, String state, int zipCode, String country)
{
this.firstName=firstName;
this.lastName=lastName;
this.homePhone=homePhone;
this.workPhone=workPhone;
this.cellPhone=cellPhone;
this.email=email;
this.streetAddress=streetAddress;
this.city=city;
this.state=state;
this.zipCode=zipCode;
this.country=country;
}

public String getFirstName()
{
return firstName;
}

public String getLastName()
{
return lastName;
}

public String getHomePhone()
{
return homePhone;
}

public String getWorkPhone()
{
return workPhone;
}

public String getCellPhone()
{
return cellPhone;
}

public String getEmail()
{
return email;
}

public String getStreetAddress()
{
return streetAddress;
}

public String getCity()
{
return city;
}

public String getState()
{
return state;
}

public int getZipCode()
{
return zipCode;
}

public String getCountry()
{
return country;
}

public int compareTo(Contact c)
{
return getLastName().compareTo(c.getLastName());
}


public String toString()
{
return "First name:\t"+firstName+"\n"+"Last name:\t"+lastName+"\n"+
"Home phone #:\t"+homePhone+"\n"+"Work phone #:\t"+workPhone+"\n"+
"Cell phone #:\t"+cellPhone+"\n"+"Email:\t\t"+email+"\n"+"Street address:\t"+
streetAddress+"\n"+"City:\t\t"+city+"\n"+"State:\t\t"+state+"\n"+ "Zip code:\t"+
zipCode+"\n"+"Country:\t"+country+"\n";
}
}


class Driver
{

private Scanner input = new Scanner(System.in);
private String firstName;
private String lastName;
private String homePhone;
private String workPhone;
private String cellPhone;
private String email;
private String streetAddress;
private String city;
private String state;
private int zipCode;
private String country;
private int menuChoice=0;
private String searchKey;
private int searchMenu;
public LinkList list = new LinkList();

public void mainMenu() throws IOException
{
readFile();

do
{
System.out.println("1: Enter contact information");
System.out.println("2: Search for a contact");
System.out.println("3: View all contacts");
System.out.println("4: Exit");
System.out.print("What would you like to do? ");
try
{
menuChoice=Integer.parseInt(input.nextLine());
System.out.println();
}
catch (NumberFormatException nfe)
{
System.out.println();
System.out.println("That is not a valid entry. Please type an integer between 1 and 4.");
System.out.println();
mainMenu();
}

if (menuChoice==1)
enterInfo();
else if (menuChoice ==2)
searchContacts();
else if (menuChoice ==3)
viewContacts();
}
while (menuChoice !=4);
}

public void enterInfo() throws IOException
{
System.out.print("First name:\t\t");
firstName= input.nextLine();
System.out.print("Last name:\t\t");
lastName= input.nextLine();
System.out.print("Home phone #:\t");
homePhone=input.nextLine();
System.out.print("Work phone #:\t");
workPhone=input.nextLine();
System.out.print("Cell phone #:\t");
cellPhone=input.nextLine();
System.out.print("Email:\t\t\t");
email=input.nextLine();
System.out.print("Street address:\t");
streetAddress=input.nextLine();
System.out.print("City:\t\t\t");
city=input.nextLine();
System.out.print("State:\t\t\t");
state=input.nextLine();
System.out.print("Zip code:\t\t");
try
{
zipCode=Integer.parseInt(input.nextLine());
System.out.print("Country:\t\t");
country=input.nextLine();
Contact person = new Contact(firstName, lastName,
homePhone, workPhone, cellPhone, email, streetAddress,
city, state, zipCode, country);
list.add(person);
System.out.println();
sortContacts();
writeFile();
System.out.println();
}
catch (NumberFormatException nfe)
{
System.out.println();
System.out.println("That is not a valid entry. Please enter a five digit zid code next time.");
System.out.println();
enterInfo();
}

}


public void sortContacts() throws IOException
{


System.out.println("Sorted.");
writeFile();
}

public void searchContacts()
{
System.out.println("For what would you like to search?");
System.out.println("1: First name");
System.out.println("2: Last name");
System.out.print("Type in your choice: ");
try
{
searchMenu=Integer.parseInt(input.nextLine());
System.out.println();
}
catch (NumberFormatException nfe)
{
System.out.println();
System.out.println("That is not a valid entry. Please type either 1 or 2.");
System.out.println();
searchContacts();
}


if(searchMenu==1)
{
System.out.print("For what first name would you like to search?");
searchKey=input.nextLine();
searchFirstName(searchKey);
}
else if(searchMenu==2)
{
System.out.print("For what last name would you like to search?");
searchKey=input.nextLine();
searchLastName(searchKey);
}
else if (searchMenu!=1 && searchMenu!=2)
{
System.out.println();
System.out.println("That is not a valid entry. Please type either 1 or 2.");
System.out.println();
searchContacts();
}



}


public void searchFirstName(String name)
{

//read in name
list.searchFirstName(name);


}

public void searchLastName(String name)
{
list.searchLastName(name);
}

public void viewContacts()
{

list.viewAll();

}

public void writeFile()throws IOException
{

list.writeToFile();


}

public void readFile()throws IOException
{
int newIndex = 0;

try
{
Scanner reader = new Scanner(new File("Contacts.dat"));
while( reader.hasNext() )
{
firstName = reader.nextLine();
lastName = reader.nextLine();
homePhone = reader.nextLine();
workPhone = reader.nextLine();
cellPhone = reader.nextLine();
email = reader.nextLine();
streetAddress = reader.nextLine();
city = reader.nextLine();
state = reader.nextLine();
zipCode = reader.nextInt();
reader.nextLine();
country = reader.nextLine();
Contact temp = new Contact (firstName, lastName,
homePhone, workPhone, cellPhone, email, streetAddress,
city, state, zipCode, country);

list.add(temp);


}
reader.close();
}
catch (FileNotFoundException e)
{
System.out.println("Sorry" + e.getMessage());
}
}
}

class LinkList
{
private ListNode front;
private ListNode back;

public LinkList()
{
front = null;
back = null;
}

public void addFirst(Comparable temp)
{
front = new ListNode(temp, front);
if(back == null)
back = front;
}

public void add(Comparable temp)
{
if(front == null)
addFirst(temp);
else
{
ListNode temp1 = back;
back = new ListNode(temp, null);
temp1.setNext(back);
}

}
public boolean remove (Contact temp)
{
ListNode current = front;
ListNode previous = front;
while(current != null)
{
previous = current;
current = current.getNext();
if (current.getValue().equals(temp))
{
previous.setNext(current.getNext());
current = null;
return true;
}
}
return false;
}
public String toString()
{
String temp = "";
ListNode p = front;
while (p!=null)
{
temp += p.getValue() + "";
p=p.getNext();
}
return temp;
}

public boolean empty()
{
return (front == null);
}
public void writeToFile()throws IOException
{
FileWriter writer = new FileWriter(new File("Contacts.dat"));
out.println("writing");
ListNode current = front;
while(current.getNext()!=null)

{

String temp2 = ((Contact)current.getValue()).getFirstName();
writer.write( temp2 + "\n");
temp2 = ((Contact)current.getValue()).getLastName();
writer.write( temp2 + "\n" );
temp2 = ((Contact)current.getValue()).getHomePhone();
writer.write( temp2 + "\n" );
temp2 = ((Contact)current.getValue()).getWorkPhone();
writer.write( temp2 + "\n" );
temp2 = ((Contact)current.getValue()).getCellPhone();
writer.write( temp2 + "\n" );
temp2 = ((Contact)current.getValue()).getEmail();
writer.write( temp2 + "\n" );
temp2 = ((Contact)current.getValue()).getStreetAddress();
writer.write( temp2 + "\n" );
temp2 = ((Contact)current.getValue()).getCity();
writer.write( temp2 + "\n" );
temp2 = ((Contact)current.getValue()).getState();
writer.write( temp2 + "\n" );
int temp = ((Contact)current.getValue()).getZipCode();
writer.write( temp + "\n" );
temp2 = ((Contact)current.getValue()).getCountry();
writer.write( temp2 + "\n" );
current=current.getNext();
}
System.out.println("Your contact information has been entered.");
writer.flush();
writer.close();
}

public void viewAll()
{
ListNode current = front;
while(current.getNext()!=null)

{
out.println(((Contact)current.getValue()).getFirstName());

out.println(((Contact)current.getValue()).getLastName());

out.println(((Contact)current.getValue()).getHomePhone());

out.println(((Contact)current.getValue()).getWorkPhone());

out.println(((Contact)current.getValue()).getCellPhone());

out.println(((Contact)current.getValue()).getEmail());

out.println(((Contact)current.getValue()).getStreetAddress());

out.println(((Contact)current.getValue()).getCity());

out.println(((Contact)current.getValue()).getState());

out.println(((Contact)current.getValue()).getZipCode());

out.println(((Contact)current.getValue()).getCountry());
//writer.write( temp1 + "\n" );

}
}

public Contact searchLastName(String search)
{
ListNode current = front;
while(current.getNext()!= null)
{ Contact temp = (Contact)current.getValue();
if(temp.getLastName().toLowerCase().equals(search.toLowerCase()))
{
return temp;


}
current=current.getNext();
}
return null;
}


public Contact searchFirstName(String search)
{
ListNode current = front;
while(current.getNext()!= null)
{ Contact temp = (Contact)current.getValue();
if(temp.getFirstName().toLowerCase().equals(search.toLowerCase()))
{
return temp;


}
current=current.getNext();
}
return null;
}//1528 idyllwild dr.

}
class ListNode implements Linkable
{
private Comparable value; // AP uses Object
private ListNode next;

public ListNode()
{
value = null;
next = null;
}

public ListNode(Comparable initValue, ListNode initNext)
{
value=initValue;
next=initNext;
}

public Comparable getValue()
{
return value;
}

public ListNode getNext()
{
return next;
}

public void setValue(Comparable theNewValue)
{
value = theNewValue;
}

public void setNext(Linkable theNewNext)
{
next = (ListNode)theNewNext;
}
}
interface Linkable
{
Comparable getValue();
Linkable getNext();
void setNext(Linkable next);
void setValue(Comparable value);
}

[wildfrog]

Explain to yourself (over and over again) what this line in your writeToFile function does:

while(current.getNext()!=null)

- petter

[Londbrok]

Initial look...

You have issues with instace variable front. Use of it makes little sense to me, it is set to null, in most cases it processing in your LinkList cannot proceed, because of that. Having taken a small peek, the only place front is ever set to not null is add(...) method, which cannot occur if there is no file to read from. or the file is empty.

If you rely so much on single instance varible, you need to be especially carefull of what values it can have. Now, if the front variable does not get inital values read in through add(..) most of the LinkList, and thus saving end of the apps IO is just sitting duck.

Fundamentally this is a common mistake. Coders tend to progress from application skeleton to test data, and then forget the case, of not having the data, since the data was allways there.

In my humble opinion... do not make so many inner classes. They are handy when needed, tricky always. You have better licence with Anonymous inner classes. but even there prudence is golden.

will take a closer look at a better time.

[Londbrok]

The linkedList class is simply not there. If you are trying to implement a node based linkedlist, that you can travel back and forth, this does not cut it.

The most critical thing, is that the chain cannot be broken at any point. Else the list simply becomes useless and unreliable. To do this, you need to maintain following rules.

- First element has no parent.
- Last element has no children.
- Every element in between has both parent and children.
- next() returns this.child
- previous() return this.parent

if these guidelines are followed, you have a basically succesfull list. If you explore the code, you will notice that eg. adding elements to the list does not preserve these rules. Then code in the LinkList tries to compensate for ListNode´s shortcomings, that simply makes things more of a mess.