Java JDBC MySQL exception: "Operation not allowed after ResultSet closed"

Solution 1:

When you run the Delete query, you use the same Statement that was used in the Select query. When you re-execute on the same Statement, the previous ResultSet gets closed.

To avoid this, you should create a new Statement everytime you execute a query. So remove statement = connection.createStatement(); from the connect() method in MySQLDatabase class, and replace all statement in that class to connection.createStatement(). You may also choose to delete the private variable statement altogether.

You can read more about it here.

Solution 2:

this error is some time occur when we use same statement object for diff. types

check Statement objectsss;