LList.java

/*
    LList.java
    David Klick
    CIS 260
    2/2/2005

Implementation of a linked list class where each node holds
    just an integer.
*/

public class LList {
    private class LNode {
        public int data;
        public LNode next;
        public LNode(int val) {
            next = null;
            data = val;
        }
    }

private LNode first = null;
    private int numElements = 0;

public LList() {
        first = null;
        numElements = 0;
    }

public void clear() throws MyListException {
        while (!isEmpty()) removeFirst();
    }

public LNode addFirst(int n) {
        LNode ln = new LNode(n);
        ln.next = first;
        first = ln;
        numElements++;
        return ln;
    }

public LNode addLast(int val) throws MyListException {
        return add(size(), val);
    }

public LNode add(int val) throws MyListException {
        return addLast(val);
    }

public LNode add(int ndx, int val) throws MyListException {
        if (ndx == 0) return addFirst(val);
        LNode ln = new LNode(val);
        LNode current = first;
        LNode previous = null;
        while ((current != null) && (ndx > 0)) {
            previous = current;
            current = current.next;
            --ndx;
        }
        if (ndx > 0) throw new MyListException("Invalid index");
        ln.next = current;
        previous.next = ln;
        numElements++;
        return ln;
    }

public int get(int ndx) throws MyListException {
        if (first == null) throw new MyListException("Empty list");
        LNode current = first;
        while ((current != null) && (ndx > 0)) {
            current = current.next;
            --ndx;
        }
        if (ndx > 0) throw new MyListException("Invalid index");
        return current.data;
    }

public int getFirst() throws MyListException {
        return get(0);
    }

public int getLast() throws MyListException {
        return get(size()-1);
    }
      
    public int removeFirst() throws MyListException {
        return remove(0);
    }

public int removeLast() throws MyListException {
        return remove(size()-1);
    }

public int remove(int ndx) throws MyListException {
        if (first == null) throw new MyListException("Empty list");
        if (ndx < 0) throw new MyListException("Invalid index specified");
        LNode current = first;
        LNode previous = null;
        while ((current.next != null) && (ndx > 0)) {
            previous = current;
            current = current.next;
            --ndx;
        }
        if (ndx > 0) throw new MyListException("Index not found in list");
        int val = current.data;
        if (current == first) first = current.next;
        else previous.next = current.next;
        numElements--;
        return val;
    }

public boolean isEmpty() { return (numElements == 0); }

public int size() { return numElements; }

public int indexOf(int val) {
        int ndx = -1;
        LNode current = first;
        while (current != null) {
            ndx++;
            if (val == current.data) return ndx;
            current = current.next;
        }
        return -1;
    }

public String toString() {
        String s = new String();
        if (first == null) s += "List is empty";
        else {
            s += "List: ";
            LNode current = first;
            s += Integer.toString(current.data);
            while (current.next != null) {
                current = current.next;
                s += ", " + Integer.toString(current.data);
            }
        }
        return s;
    }
}

class MyListException extends Exception {
    public MyListException() {}
    public MyListException(String msg) { super(msg); }
}