Cachofonia

public static class Cacher {
        private static final ConcurrentSkipListMap<CacherKey, Integer> cache = new ConcurrentSkipListMap<CacherKey, Integer>();

        public void put(String key, Integer value) {
            if (cache.size() >= 10) {
                cache.pollLastEntry();
            }
            cache.put(new CacherKey(System.currentTimeMillis(), key), value);
        }

        public static class CacherKey implements Comparable<CacherKey> {
            public final Long ts;
            public final String key;

            public CacherKey(Long ts, String key) {
                this.ts = ts;
                this.key = key;
            }

            @Override
            public boolean equals(Object o) {
                if (this == o) return true;
                if (o == null || getClass() != o.getClass()) return false;

                CacherKey cacherKey = (CacherKey) o;

                return key != null ? key.equals(cacherKey.key) : cacherKey.key == null;

            }

            @Override
            public int hashCode() {
                return key != null ? key.hashCode() : 0;
            }

            @Override
            public int compareTo(CacherKey other) {
                if (other.key.equals(key)){
                    return 0;
                }

                if (other.ts < ts) {
                    return -1;
                } else if (other.ts > ts) {
                    return 1;
                } else {
                    return 0;
                }
            }

            @Override
            public String toString() {
                return "CacherKey{" +
                        "ts=" + ts +
                        ", key='" + key + '\'' +
                        '}';
            }
        }

        public ConcurrentSkipListMap<CacherKey, Integer> getCache() {
            return cache;
        }

        public static void main(String[] args) throws InterruptedException {
            ConcurrentSkipListMap<String, Integer> vv = new ConcurrentSkipListMap<String, Integer>();
            vv.put("1", 1);
            vv.put("1", 1);
            vv.put("1", 1);
            System.out.println(vv.size());

            Cacher c = new Cacher();
            c.put("1", 1);
            pause();
            c.put("2", 2);
            pause();
            c.put("3", 3);

            for (Integer i = 1; i < 4; i++) {
                pause();
                c.put(i.toString(), i);
            }

            for (Map.Entry<CacherKey, Integer> entry : c.getCache().entrySet()) {
                System.out.println("Key: " + entry.getKey() + ", value: " + entry.getValue());
            }
        }

        private static void pause() throws InterruptedException {
            Thread.currentThread().sleep(3);
        }
    }

Key: CacherKey{ts=1470069695879, key='3'}, value: 3
Key: CacherKey{ts=1470069695876, key='2'}, value: 2
Key: CacherKey{ts=1470069695872, key='1'}, value: 1
Key: CacherKey{ts=1470069695864, key='3'}, value: 3
Key: CacherKey{ts=1470069695860, key='2'}, value: 2
Key: CacherKey{ts=1470069695857, key='1'}, value: 1