concurrency general strategy

synchronized(this){
  Connection con = connectionMap.getByIp(ip);
  if (con == null) {
     con = new ConnectionFactory.createConn(..);
     connectionMap.put(con);
  }
  try {
    con.connect()  // long-lasting job
  } catch (Exception e) { 
     connectionMap.remove(con);
  }
}

Is there a strategy that we can apply to remove connect() out of the synchronized block for performance consideration?

The solution is to split one big lock into n + 1 small locks. n small locks on each Connection object and one lock on the ConnectionMap. Java 5's ReentrantLock (trylock())can be used to implement non-blocking mechanism.