I am having trouble adding information from a ".txt" file to a linked list... here is what i have.
list1.txt:
1 2 4 5 6 7 8 11
/**
The LinkedList1 class implements a Linked list.
*/
class LinkedList1
{
/**
The Node class stores a list element
and a reference to the next node.
*/
private class Node
{
String value;
Node next;
/**
Constructor.
@param val The element to store in the node.
@param n The reference to the successor node.
*/
Node(String val, Node n)
{
value = val;
next = n;
}
/**
Constructor.
@param val The element to store in the node.
*/
Node(String val)
{
// Call the other (sister) constructor.
this(val, null);
}
}
private Node first; // list head
private Node last; // last element in list
/**
Constructor.
*/
public LinkedList1()
{
first = null;
last = null;
}
/**
The isEmpty method checks to see
if the list is empty.
@return true if list is empty,
false otherwise.
*/
public boolean isEmpty()
{
return first == null;
}
/**
The size method returns the length of the list.
@return The number of elements in the list.
*/
public int size()
{
int count = 0;
Node p = first;
while (p != null)
{
// There is an element at p
count ++;
p = p.next;
}
return count;
}
/**
The add method adds an element to
the end of the list.
@param e The value to add to the
end of the list.
*/
public void add(String e)
{
if (isEmpty())
{
first = new Node(e);
last = first;
}
else
{
// Add to end of existing list
last.next = new Node(e);
last = last.next;
}
}
/**
The add method adds an element at a position.
@param e The element to add to the list.
@param index The position at which to add
the element.
@exception IndexOutOfBoundsException When
index is out of bounds.
*/
public void add(int index, String e)
{
if (index < 0 || index > size())
{
String message = String.valueOf(index);
throw new IndexOutOfBoundsException(message);
}
// Index is at least 0
if (index == 0)
{
// New element goes at beginning
first = new Node(e, first);
if (last == null)
last = first;
return;
}
// Set a reference pred to point to the node that
// will be the predecessor of the new node
Node pred = first;
for (int k = 1; k <= index - 1; k++)
{
pred = pred.next;
}
// Splice in a node containing the new element
pred.next = new Node(e, pred.next);
// Is there a new last element ?
if (pred.next.next == null)
last = pred.next;
}
/**
The toString method computes the string
representation of the list.
@return The string form of the list.
*/
public String toString()
{
StringBuilder strBuilder = new StringBuilder();
// Use p to walk down the linked list
Node p = first;
while (p != null)
{
strBuilder.append(p.value + "\n");
p = p.next;
}
return strBuilder.toString();
}
/**
The remove method removes the element at an index.
@param index The index of the element to remove.
@return The element removed.
@exception IndexOutOfBoundsException When index is
out of bounds.
*/
public String remove(int index)
{
if (index < 0 || index >= size())
{
String message = String.valueOf(index);
throw new IndexOutOfBoundsException(message);
}
String element; // The element to return
if (index == 0)
{
// Removal of first item in the list
element = first.value;
first = first.next;
if (first == null)
last = null;
}
else
{
// To remove an element other than the first,
// find the predecessor of the element to
// be removed.
Node pred = first;
// Move pred forward index - 1 times
for (int k = 1; k <= index -1; k++)
pred = pred.next;
// Store the value to return
element = pred.next.value;
// Route link around the node to be removed
pred.next = pred.next.next;
// Check if pred is now last
if (pred.next == null)
last = pred;
}
return element;
}
/**
The remove method removes an element.
@param element The element to remove.
@return true if the remove succeeded,
false otherwise.
*/
public boolean remove(String element)
{
if (isEmpty())
return false;
if (element.equals(first.value))
{
// Removal of first item in the list
first = first.next;
if (first == null)
last = null;
return true;
}
// Find the predecessor of the element to remove
Node pred = first;
while (pred.next != null &&
!pred.next.value.equals(element))
{
pred = pred.next;
}
// pred.next == null OR pred.next.value is element
if (pred.next == null)
return false;
// pred.next.value is element
pred.next = pred.next.next;
// Check if pred is now last
if (pred.next == null)
last = pred;
return true;
}
public static void main(String [] args)
{
LinkedList1 ll = new LinkedList1();
ll.add("Amy");
ll.add("Bob");
ll.add(0, "Al");
ll.add(2, "Beth");
ll.add(4, "Carol");
System.out.println("The members of the list are:");
System.out.print(ll);
}
}here is the code i am trying to use inorder to read info in from A .txt file...
import java.io.*;
import java.util.Scanner;
public class ScanLinkedList {
public static void main(String[] args) throws IOException {
Scanner s = null;
try {
LinkedList1 test = new LinkedList1();
s = new Scanner(new BufferedReader(new FileReader("list1.txt")));
while (s.hasNext()) {
test.add(s.next());
test.toString();
System.out.println(s);
}
} finally {
if (s != null) {
s.close();
}
}
}
}