LRU Cache implementation with linked hash map.

LRUCache.java

package edu.sjsu.watsh.algos;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

/**
 * Implement LRU cache using linked hash map.
 *
 * @author rwatsh on 8/7/17.
 */
public class LRUCache {
    private Map<String, Object> cache = new LinkedHashMap<>();
    private int capacity = Integer.MAX_VALUE;

    public LRUCache(int capacity) {
        this.capacity = capacity;
    }

    public Object get(String key) {
        if (cache.get(key) != null) {
            Object value = cache.get(key);
            synchronized (LRUCache.class) {
                if (cache.get(key) != null) {
                    cache.remove(key);
                    cache.put(key, value);
                }
            }
            return value;
        }
        return null;
    }

    public void put(String key, Object value) {
        if (cache.get(key)  == null) {
            if (cache.size() >= capacity) {
                List<Object> list = new ArrayList<>(cache.values());
                cache.remove(list.get(0));
            }
            cache.put(key, value); // add it to the end.
        } else {
            // value exists, so remove and add it back with the updated value
            cache.remove(key);
            cache.put(key, value);
        }
    }

    @Override
    public String toString() {
        return cache.values().toString();
    }

    public static void main(String[] args) {
        LRUCache cache = new LRUCache(5);
        cache.put("1", "1");
        cache.put("2", "2");
        cache.put("3", "3");
        cache.put("4", "4");
        System.out.println(cache);
        cache.put("5", "5");
        cache.put("6", "6");
        System.out.println(cache);
        cache.get("5");
        System.out.println(cache);
        cache.get("2");
        System.out.println(cache);

    }
}