How to return false where the result of JDBC is empty

Question

In my code, i need when the result of query is empty, it should return false.

My code:

public boolean user_bookValidationQuery(String userID, String bookID) {
    Connection con;    
    PreparedStatement ps;    
    String query = " select * from borrowed where userID=? and bookID=? ";    
    try {    
        con = DriverManager.getConnection(...);    
        ps = con.prepareStatement(query);    
        ps.setString(1, userID);    
        ps.setString(2, bookID);
        if (ps.execute()) {
            System.out.println("You can do it! , id DB");
            return true;
        } else return false;

    } catch (SQLException sqle) {
        sqle.printStackTrace();
        return false;
    }
}

Now for a give value for userID and bookID , i try in mysql console and see that it's result was empty, But in my code it return true still!

Why not false here?

Answer 1

you need to check the result of the statement ...

ResultSet rs= ps.execute();
rs.isBeforeFirst()

will returns false if there are no rows in the ResultSet

so your code should look like this :

try {
    con = DriverManager.getConnection(...);
    ps = con.prepareStatement(query);
    ps.setString(1, userID);
    ps.setString(2, bookID);
    ResultSet rs= ps.execute();

    if (!rs.isBeforeFirst() ) {    
          System.out.println("empty"); 
          return false;
    }else {
          System.out.println("with data"); 
          return true;
    }

} catch (SQLException sqle) {
    sqle.printStackTrace();
    return false;
}