Boolean method is returning true everytime

Question

I'm using SQL to compare a date of an event

public static boolean sameDate(String DateString)
{

   PreparedStatement statement = Application.database.newStatement("SELECT * FROM BookShift WHERE id = ?  IN (SELECT id FROM Class WHERE Date  = ?)"); 

    try 
    {
       if(statement !=null)
       {
           statement.setInt(1, main.id);
           statement.setString(2, DateTwo);

           ResultSet results = Application.database.runQuery(statement);

           if (results != null)
           {
               return true;
           }
           else {
            return false;
            }
        }
    }
    catch (SQLException resultsexception)
   {
        System.out.println("Database result processing error: " + resultsexception.getMessage());
    }
    return false;
   }

Whenever I run my program and try booking a new shift, regardless of whether it does clash or not it always returns that it does.

Answer 1

You need to check if the result set has any rows or not, not check if it is null.

 if (results.next())
 {
     return true;
 }
 else {
     return false;
 }

or, of course, just

return results.next();

Answer 2

As the comments say, it is not generally correct to check if results is null. I don't have the SQL experience to tell you what runQuery() will return on a query that fails, but I doubt that it's null, I would expect it to return an empty ResultSet .

Checking if it's null first isn't a bad thing, and in fact is a good idea to avoid NullPointerException throws. However, it's not enough to just use that check.