Two ways to invoke Oracle function in Java ____c++

1.

preparedstatement stmt =conn.preparestatement ("Select Pkg.fun" (?) from dual ");

Stmt.setlong (1,123);

Result rs = Stmt.executequery ();

if (rs.next) {return

   rs.getdouble (1);

}

2.

callablestatement Stmt=conn.preparecall ("{=call pkg.fun (?)}");

Stmt.registeroutparameter (1,java.sql.types.double);

Stmt.setlong (2,123);

if (!stmt.execute ()) {return

   stmt.getdouble (1);

}

The information found below from the Web

callablestatement.execute ()

returns a Boolean value ... Returns

true if the first value returned is ResultSet, otherwise returns false ...

finally understand why the execution success also returns false.

Both ways are fine, but the second way looks normal.