Re: array of references to linked lists

Question

Hi, im having a little problem seeing the wood from the tree...shouldnt be too hard for a fresh pair of eyes...ive been trying for a while now(read ages !!).
I have an array which will be populated with seperate linked lists (StudentList class) which are populated from a console interface (prompt).
It seems to work fine, however .. each list entered will overwrite the last by adding itself to it. eg :
list 1 is added : adam 998 albert 999
list 2 is added : john 123 jill 666
lists[0].print() : jill 666 john 123 albert 999 adam 998
lists[1].print() : jill 666 john 123 albert 999 adam 998
it should give
lists[0].print() : jill 666 john 123
lists[1].print() : albert 999 adam 998
the code is below,
cheers for ANY help,
ta.
import java.io.*;
import java.util.*;
public class StudentId {
     public static void main(java.lang.String[] args) {
          StudentList[] lists = new StudentList[20];
          for (int i = 0; i < lists.length; i++) {
               lists[i] = new StudentList();
          int n = 0;
          BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
          for(;;) {
               System.out.print("Please enter a student record list> ");
               try {
                    //StudentList list = new StudentList();
                    String line = in.readLine();
                    if (line.equals("quit")) {
                         break;
                    StringTokenizer tokenBag = new StringTokenizer (line," ");
                    while (tokenBag.hasMoreTokens()) {
                         try {
                              String name = tokenBag.nextToken();
                              String idString = tokenBag.nextToken();
                              int id = Integer.parseInt(idString);
                              lists[n].insert(name, id);
                         catch(Exception e) {
                              System.out.println("Input error : " + e);
               catch (Exception e) {
                    System.out.println("exception : " + e);
               n += 1;
          for (int i=0; i<n; i++) {
               System.out.println("element " + i);
               lists.print();

Answer 1

other class (Int node class is standard node class altered
public class StudentList {
     private static IntNode head;
     private static int count;
     public StudentList() {
          head = null;
          count = 0;
     public boolean isEmpty() {
          if (count == 0) return true;
          else return false;
     public int size(){
          return count;
    public IntNode getHead() {
          return head;
     public void printHead() {
          System.out.println(head.getName() + " " + head.getId());
     public IntNode getTail() {
          IntNode cursor;
          for (cursor = head; cursor != null; cursor = cursor.getLink()) {
          return cursor;
     public void insert(String name, int id){
          head = new IntNode(name, id ,head);
          count++;
     public IntNode searchFor(String name) {
          IntNode cursor;
          cursor = head.listSearch(head, name);
          return cursor;
     public IntNode searchFor(int id) {
          IntNode cursor;
          cursor = head.listSearch(head, id);
          return cursor;
     public void print() {
          IntNode cursor = head;
          for (int i=0; i<count; i++) {
               System.out.println(cursor.getName()+" "+cursor.getId());
               cursor = cursor.getLink();
     public void insertListBefore(IntNode match, StudentList list) {
          IntNode preCursor = head.getPrevious(head, match);
          IntNode cursor;
          cursor = this.searchFor(match.getName());
          preCursor.setLink(list.getHead());
          list.getTail().setLink(cursor);
}