Solutions to the Try It Out Exercises in Java For Dummies, 8th Edition
by Barry Burd

Chapter 17: Using Java Database Connectivity

In this chapter:

• High Rollers Only
• Watch Your Primary Key
• Not Too Taxing

High Rollers Only

Watch Your Primary Key

The first time you run the AddData program, you add a row with the name Barry Burd to the table. That's okay. But the second time you run the AddData program, you try to add a second row with the same name Barry Burd to the table. But since NAME is a primary key, having two rows with the same NAME (Barry Burd) is not allowed. So the program refuses to add the data.

Not Too Taxing

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class CreateTable {

    public static void main(String args[]) {

        final String CONNECTION = "jdbc:sqlite:AccountDatabase.db";

        try (Connection conn = DriverManager.getConnection(CONNECTION);
            var statement = conn.createStatement()) {

            statement.executeUpdate("""
                    create table ITEMS
                    (NAME VARCHAR(32) NOT NULL PRIMARY KEY,
                    PRICE FLOAT,
                    TAXRATE FLOAT)""");
            System.out.println("ITEMS table created.");

        } catch (SQLException e) {
            System.out.println(e.getMessage());
        }
    }
}


import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class AddData {

    public static void main(String args[]) {

        final String CONNECTION = "jdbc:sqlite:AccountDatabase.db";

        try (Connection conn = DriverManager.getConnection(CONNECTION);
            var statement = conn.createStatement()) {

            statement.executeUpdate("""
                    insert into ITEMS values
                    ('Food', 10.00, 0.05)""");

            statement.executeUpdate("""
                    insert into ITEMS values
                    ('Clothing', 20.00, 0.07)""");

            System.out.println("Rows added.");

        } catch (SQLException e) {
            System.out.println(e.getMessage());
        }
    }
}


import static java.lang.System.out;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.text.NumberFormat;

public class GetData {

    public static void main(String args[]) {
        NumberFormat currency = NumberFormat.getCurrencyInstance();
        final String CONNECTION = "jdbc:sqlite:AccountDatabase.db";

        try (Connection conn = DriverManager.getConnection(CONNECTION);
             var statement = conn.createStatement();
             var resultset =
                     statement.executeQuery("select * from ITEMS")) {

            while (resultset.next()) {
                out.print(resultset.getString("NAME"));
                out.print(", ");
                double price = resultset.getFloat("PRICE");
                double taxRate = resultset.getFloat("TAXRATE");
                out.println(currency.format(price * (1 + taxRate)));
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class DropTable {

    public static void main(String[] args) {
        final String CONNECTION = "jdbc:sqlite:AccountDatabase.db";

        try (Connection conn = DriverManager.getConnection(CONNECTION);
            var statement = conn.createStatement()) {

            statement.executeUpdate("drop table ITEMS");

            System.out.println("ITEMS table dropped.");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}