SoftReferenceMap

Cache.java

    public class Cache<K, V> {

        private final Map<K, SoftReference<V>> map;

        public Cache(final int cacheSize) {
            map = Collections.synchronizedMap(new LinkedHashMap<K, SoftReference<V>>() {

                @Override
                protected boolean removeEldestEntry(java.util.Map.Entry<K, SoftReference<V>> eldest) {
                    return size() > cacheSize;
                }
            });
        }

        public V put(K key, V value) {
            SoftReference<V> previousValue = map.put(key, new SoftReference<V>(value));
            return previousValue != null ? previousValue.get() : null;
        }

        public V get(K key) {
            SoftReference<V> valueReference = map.get(key);
            return valueReference != null ? valueReference.get() : null;
        }
    }