Re: Warning unchecked call
On Fri, 22 Jan 2010 02:31:43 -0800, jc_usernet wrote:
Hello.
I am adding a simple method to a class for db access. It is to copy a
column of data from a ResultSet class to a Vector class object. It
works but I get a compile warning which I wish I knew how to remove. The
message is;
------------------------------------------------------------
ResultSetTableModel.java:175: warning: [unchecked] unchecked call to
add(E) as a member of the raw type java.util.Vector
v.add( resultSet.getInt(colName) );
------------------------------------------------------------
The compiler is warning you that it cannot check that what you are adding
to the Vector is of the correct class. Presumably you have declared the
Vector without specifying what class it should contain.
and the method I have added is
------------------------------------------------------------ // new
method by JC
// obtain a column into a vector for a string column public Vector
getVectorFrmStringColumn( String colName )
throws IllegalStateException
{
Vector v = new Vector();
You have declared an untyped Vector. This Vector can contain anything,
the compiler is unable to verify that what you add to it is of the
correct type. So, the compiler will warn you every time you add something
to it that its type is unchecked.
// ensure database connection is available if ( !connectedToDatabase
)
throw new IllegalStateException( "Not Connected to
Database" );
// obtain a string column specified by colName try {
//System.out.println(" Before vector"); resultSet.beforeFirst();
while ( resultSet.next() ) {
v.add( resultSet.getString(colName) ); // this is line
175
}
}
catch( SQLException sqlException ) {
System.out.println( "sqlException occurred.");
sqlException.printStackTrace();
}
catch(Exception xception ) {
System.out.println(" The unknown exception ");
System.out.println( xception.toString() );
}
return v;
}
------------------------------------------------------------
How do I get rid of this warning ?
If the Vector is only supposed to contain objects of a particular type
then specify that in its declaration. In this case it looks like it only
holds Strings. If you declare it as:
Vector<String> v = new Vector<String>();
the compiler knows that your Vector should only contain Strings. It can
check this for you and the add() is no longer unchecked.
If the Vector really can contain objects of more than one type then you
can suppress the warning using @SuppressWarnings("unchecked") for that
method. But this is a blunt instrument and can mask problems which the
compiler would otherwise have told you about.
Is it the process of handling an unchecked exception ?
No, unchecked exceptions are entirely unrelated. They are a specific
subset of Exception which are not required to be caught, or declared as
being thrown, by a method.
--
Nigel Wade