java/W8/Cache.java

import java.util.HashMap;
import java.util.Map;

public class Cache<K, V> {
    private Map<K, V> cacheMap;
    private int maxSize;

    public Cache() {
        this.cacheMap = new HashMap<>();
        this.maxSize = Integer.MAX_VALUE;
    }

    public Cache(int maxSize) {
        this.cacheMap = new HashMap<>();
        this.maxSize = maxSize;
    }

    public void put(K key, V value) {
        if (cacheMap.size() >= maxSize) {
            K firstKey = cacheMap.keySet().iterator().next();
            cacheMap.remove(firstKey);
        }
        cacheMap.put(key, value);
    }

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

    public boolean containsKey(K key) {
        return cacheMap.containsKey(key);
    }

    public V remove(K key) {
        return cacheMap.remove(key);
    }

    public int size() {
        return cacheMap.size();
    }

    public void clear() {
        cacheMap.clear();
    }

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

    public static void main(String[] args) {
        Cache<String, Integer> cache = new Cache<>(3);
        cache.put("A", 1);
        cache.put("B", 2);
        cache.put("C", 3);
        System.out.println("Cache after adding A,B,C: " + cache);
        
        cache.put("D", 4);
        System.out.println("Cache after adding D (maxSize=3): " + cache);
        
        System.out.println("Get B: " + cache.get("B"));
        System.out.println("Contains C: " + cache.containsKey("C"));
        System.out.println("Size: " + cache.size());
    }
}