Re: enums, using methods as initializers
Daniel Pitts wrote:
I very much try to avoid switch (or if/elseif/elesif,etc..) as much as
feasible.
Switch is a remnant of procedural programming languages. Often times it
was used to create polymorphic behavior based on a "type" token. Well,
now you have a "type" that can do that polymorphic behavior for you.
I'm not saying there are NEVER times when you can use switch statements,
I'm just saying that by the time I need one switch statement, I probably
need two, and at that point its time to use polymorphism and create an
abstract method for each of my switch statements. As a mater of fact, I
would *love* a tool that could take an switch(enum) and convert it to
enum.method().
Hear that JetBrains? Make it happen :-)
One major advantage of the polymorphic approach is that you get compiler
enforcement. You cannot "fall" into an unexpected case, or forget to
implement a behavior.
In fact, I find the quirky combination of the class attitude and the enum
constant ancestry along with the peculiarities of Java's implementation as a
pseudo-inherited Enum class with occasional implicit inner classes extending
the enum to be a strangely, emergently powerful mechanism. For one thing,
enums may hold the power to release us from the temptation to reflection.
Back to the OP's question, Daniel, were you thinking of something like this,
only maybe better refactored?
You'd use it something like:
Object val =
Noom.valueOf( rsMetaData.getColumnType( col ) )
.getValue( rs, col );
(throws NPE)
<sscce>
public enum Noom
{
BOOLEAN( Types.BOOLEAN )
{
@Override
public Boolean getValue( ResultSet rs, int column )
{
try
{
return (rs.getObject( column ) == null? null :
Boolean.valueOf( rs.getBoolean( column )));
}
catch ( SQLException ex )
{
logger.error( "SQL Exception"+ ex.getMessage(), ex );
return null;
}
}
}
,
VARCHAR( Types.VARCHAR )
{
@Override
public String getValue( ResultSet rs, int column )
{
try
{
return rs.getString( column );
}
catch ( SQLException ex )
{
logger.error( "SQL Exception"+ ex.getMessage(), ex );
return null;
}
}
}
;
private final int sqlType;
private Noom( int sqlT )
{
this.sqlType = sqlT;
}
public static Noom valueOf( int sqlT )
{
for ( Noom noom : values() )
{
if ( noom.sqlType == sqlT )
{
return noom;
}
}
return null;
}
private static final Logger logger = Logger.getLogger( Noom.class );
public abstract Object getValue( ResultSet rs, int column );
}
</sscce>
--
Lew