How to ensure thread safety of the implemented LRU cache?

To ensure thread safety of an LRU cache in Java, several approaches can be used:

1. Method synchronization — wrap all methods that modify the cache state in synchronized blocks or declare them synchronized, so that only one thread can perform operations at a time.

2. Using ConcurrentHashMap and ConcurrentLinkedDeque — for storing data and access order, which helps avoid locks at the entire cache level.

3. Using ready-made thread-safe data structures — for example, LinkedHashMap with an overridden removeEldestEntry method can be wrapped in Collections.synchronizedMap, but additional synchronization of iterations is needed.

4. Using ReentrantLock — a more flexible locking mechanism that allows controlling access and avoiding performance issues.

Example with synchronized methods:

public class ThreadSafeLRUCache<K, V> {
    private final int capacity;
    private final LinkedHashMap<K, V> cache;

    public ThreadSafeLRUCache(int capacity) {
        this.capacity = capacity;
        this.cache = new LinkedHashMap<K, V>(capacity, 0.75f, true) {
            protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
                return size() > ThreadSafeLRUCache.this.capacity;
            }
        };
    }

    public synchronized V get(K key) {
        return cache.get(key);
    }

    public synchronized void put(K key, V value) {
        cache.put(key, value);
    }
}

This approach guarantees that get and put operations will not be executed simultaneously from different threads, preventing race conditions.