LRU (Least Recently Used) Cache

LRUCache.java

public class LRUCache {
    private int capacity;
    private Map<Integer, Integer> cache;
    private LinkedHashMap<Integer, Long> accessTime;
    
    public LRUCache(int capacity) {
        this.capacity = capacity;
        this.cache = new HashMap<>();
        this.accessTime = new LinkedHashMap<>();
    }
    
    public int get(int key) {
        if (!cache.containsKey(key)) {
            return -1;
        }
        accessTime.put(key, System.nanoTime());
        return cache.get(key);
    }
    
    public void put(int key, int value) {
        if (cache.size() >= capacity) {
            long oldestTime = Long.MAX_VALUE;
            int oldestKey = -1;
            for (Map.Entry<Integer, Long> entry : accessTime.entrySet()) {
                if (entry.getValue() < oldestTime) {
                    oldestTime = entry.getValue();
                    oldestKey = entry.getKey();
                }
            }
            cache.remove(oldestKey);
            accessTime.remove(oldestKey);
        }
        cache.put(key, value);
        accessTime.put(key, System.nanoTime());
    }
}