Question

Every time we implement a PooledConnection we write

class MyConnection implements PooledConnection, Connection {
  // implement methods of PooledConnection and Connection 
}

And I am wondering why PooledConnection was not designed as extends Connection? since a PooledConnection is always a Connection after all.

Answer 1

I’m by no means sure, but I imagine the reason PooledConnection doesn’t extend Connection is so that you can make a significantly simpler PooledConnection implementation that uses any other existing Connection implementation, allowing code-reuse and keeping functionality separate.