code: public void put(String key, T token) {
          purge();
          if (map.containsKey(key)) {
              map.remove(key);
          }
          final long time = System.currentTimeMillis();
          map.put(key, new Value(token, time + expireMillis));
          latestWriteTime = time;
      }
docs: Put a token in the cache.
  If a token already exists for the given key, it is replaced.
  
  @param key   The key to insert for.
  @param token The token to insert.