java.sql-ResultSet r.next（）不起作用

Question

I don't understand why ResultSet isn't working as if there are no results

public static int checkProductID(Connection conn) {

    boolean productIDisvalid = false;
    int id = 0;
    while (!productIDisvalid) {
        System.out.println("Enter a product ID: ");
        try {
            id = Integer.parseInt(readLine());
            if (id < 10000000 && id > 0) {
                System.out.println(id);
                // PreparedStatement pstmt = conn.prepareStatement ("INSERT INTO INVENTORY VALUES (?,?,?,?) ");
                // pstmt.setInt(1,4000); pstmt.setString(2,"hello"); pstmt.setInt(3,4000); pstmt.setInt(4,400);
                PreparedStatement pstmt = conn.prepareStatement("SELECT * FROM INVENTORY WHERE PRODUCTID = ?");
                pstmt.setInt(1, id);
                ResultSet r = pstmt.executeQuery();
                while (r.next()) {
                    System.out.println(r.getInt("PRODUCTID"));
                    if (r.getInt("PRODUCTID") == id) return id;
                }
            }

        } catch (NumberFormatException | SQLException | NullPointerException e) {
            e.printStackTrace();
            continue;
        }
    }

    return id;
}

I quoted out an insert values to prove it works and that it is correctly connected to the database.

The insert values works. But whenever I attempt to perform a search query on the database, it doesn't work, r.next() is never true and the print statement inside that while loop never executes, even if I change the query to "SELECT * FROM INVENTORY WHERE PRODUCTID = 1000"

Answer 1

Your problem was happening because you had not explicitly committed your insert from sqlplus. When you exit sqlplus there is an implicit commit that happens which is why the problem went away.