How do I get a Double out of a resultset instead of double?

You can check for wasNull on your ResultSet to find out if the value was null.

Note that you must first call one of the getter methods on a column to try to read its value and then call the method wasNull to see if the value read was SQL NULL.

If you really need a Double afterwards, you can create it from the double returned.

An alternative to the aforementioned ResultSet#wasNull() is to test ResultSet#getObject() on null so that you can nicely put it in a single line in combination with the ternary operator:

Double d = resultSet.getObject("column") != null ? resultSet.getDouble("column") : null;

instead of

Double d = resultSet.getDouble("column");
if (resultSet.wasNull()) {
    d = null;
}

Use ResultSet.wasNull -> http://java.sun.com/javase/6/docs/api/java/sql/ResultSet.html#wasNull%28%29

Basically it works for all primitive types, you first use getDouble, getInt, etc., and then only if the result is 0 you use wasNull.

In kotlin:

private fun ResultSet.getDoubleOrNull(columnIndex: Int): Double? when {

     this.getObject(columnIndex) == null -> null

     else -> this.getDouble(columnIndex)

}