Cache.java

package Q9_05_Cache;

import java.util.HashMap;

public class Cache {
	public static int MAX_SIZE = 10;
	public Node head;
	public Node tail;
	public HashMap<String, Node> map;
	public int size = 0;
	
	public Cache() {
		map = new HashMap<String, Node>();
	}
	
	public void moveToFront(Node node) {
		if (node == head) {
			return;
		}
		removeFromLinkedList(node);
		node.next = head;
		if (head != null) {
			head.prev = node;
		}
		head = node;
		size++;
		
		if (tail == null) {
			tail = node;
		}
	}
	
	public void moveToFront(String query) {
		Node node = map.get(query);
		moveToFront(node);
	}	
	
	public void removeFromLinkedList(Node node) {
		if (node == null) {
			return;
		}
		
		if (node.next != null || node.prev != null) {
			size--;
		}
		
		Node prev = node.prev;
		if (prev != null) {
			prev.next = node.next;
		} 
		
		Node next = node.next;
		if (next != null) {
			next.prev = prev;
		}
		
		if (node == head) {
			head = next;
		}
		
		if (node == tail) {
			tail = prev;
		}
		
		node.next = null;
		node.prev = null;
	}
	
	public String[] getResults(String query) {
		if (map.containsKey(query)) {
			Node node = map.get(query);
			moveToFront(node);
			return node.results;
		}
		return null;
	}
	
	public void insertResults(String query, String[] results) {
		if (map.containsKey(query)) {
			Node node = map.get(query);
			node.results = results;
			moveToFront(node);
			return;
		}
		
		Node node = new Node(query, results);
		moveToFront(node);
		map.put(query, node);
		
		if (size > MAX_SIZE) {
			map.remove(tail.query);
			removeFromLinkedList(tail);
		}
	}
}