DoubleLinkedList.java

package honux;

public class DoubleLinkedList {
	private Node head, tail;
	private int count;
	
	public DoubleLinkedList() {
		head = tail = null;
		count = 0;	
	}
	
	public void addFirst(int i) {
		Node n = new Node(i);
		n.next = head;
		n.prev = null;	
		head = n;
		if(tail == null)
			tail = head;
	}
	
	public void addLast(int i){
			
	}
	
	public void insert(int index) {
		
	}
	
	public int get(int index) {
		return 0;
	}
	
	public int removeFirst() {
		return 0;
	}
	
	public int removeLast() {
		return 0;
	}
	
	public int remove(int index) {
		return 0;
	}
	
	public int size() {
		return this.count;
	}
		
	public static void test(String s, boolean b) throws Exception {
		if(b==false) 
			throw new Exception(s +" assertion fail");
	}

	//python range function
	public static int[] range(int n) {
		int[] r = new int[n];
		for(int i = 0; i < n; i++) 
			r[i] = i;
		return r;
	}
	
	//simple test 
	public static void main(String[] args) throws Exception {
		DoubleLinkedList d = new DoubleLinkedList();
		
		int[] r = range(5);
		
		//test1 addFirst get
		for(int i:r) {
			d.addFirst(5 - i - 1); //0 1 2 3 4 		
		}
		
		for(int i:r) {
			test("test1", d.get(i) == i);
		}
		
		//test2 addLast	
		for(int i:r) {
			d.addLast(5 + i);
			test("test2", d.get(5 + i) == 5 + i); //0 1 2 3 4 5 6 7 8 9
		}
		
		//test3 removeFirst
		for(int i:r) {
			int n = d.removeFirst();
			test("test3", i == n);
		}	
		
		//test4 removeLast 
		//test5 
		//...
	}
}

 class Node {
	int item;
	Node prev;
	Node next;
	Node(int i) {
		this.item = i;
		prev = next = null;
	}
}