LinkedIntList.java

// Implement a linked list of integers

public class LinkedIntList {

	// first value in the list
	private ListNode front;

	// construct an empty list
	public LinkedIntList() {
		front = null;
	}

	// return number of elements in the list
	public int size() {
		int count = 0;
		ListNode current = front;
		while (current != null) {
			current = current.next;
			count++;
		}
		return count;
	}

	// return the integer at the given index. assumes 0 <= index < size()
	public int get(int index) {
		return nodeAt(index).data;
	}

	// return the position of the first occurrence of the value
	// return -1 if not found
	public int indexOf(int value) {
		int index = 0;
		ListNode current = front;
		while (current != null) {
			if (current.data == value) {
				return index;
			}
			index++;
			current = current.next;
		}
		return -1;
	}

	// append given value to the end of the list
	public void add(int value) {
		if (front == null) {
			front = new ListNode(value);
		} else {
			ListNode current = front;
			while (current.next != null) {
				current = current.next;
			}
			current.next = new ListNode(value);
		}
	}

	// inserts given value at the given index. assumes 0 <= index <= size()
	public void add(int index, int value) {
		if (index == 0) {
			front = new ListNode(value, front);
		} else {
			ListNode current = nodeAt(index - 1);
			current.next = new ListNode(value, current.next);
		}
	}

	// remove value at the given index. assumes pre : 0 <= index < size()
	public void remove(int index) {
		if (index == 0) {
			front = front.next;
		} else {
			ListNode current = nodeAt(index - 1);
			current.next = current.next.next;
		}
	}

	// helper method: return a reference to the node at the given index
	// assumes0 <= i < size()
	private ListNode nodeAt(int index) {
		ListNode current = front;
		for (int i = 0; i < index; i++) {
			current = current.next;
		}
		return current;
	}

	// create a printable version of the list
	public String toString() {
		if (front == null) {
			return "[]";
		} else {
			String result = "[" + front.data;
			ListNode current = front.next;
			while (current != null) {
				result += ", " + current.data;
				current = current.next;
			}
			result += "]";
			return result;
		}
	}

}