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Putting it together

Combine the cart class with a menu loop.

Putting the cart together

In the final lesson we combine the cart. Add a third item, list all items with for-each, add a third price and compute the total:

cart.add("Milk");
cart.set(0, "Apple x2");
cart.remove(1);
for (String item : cart) {
    System.out.println(item);
}
// ... prices and total

This is the skeleton of the cart app: adding, listing and total. Listing each item shows the cart to the customer.

Practice List all items

Add to the previous code: add a third item with cart.add("Milk") (after the first add calls). Update with cart.set(0, "Apple x2") and cart.remove(1). List all items with for (String item : cart) { System.out.println(item); }. Add a third price with prices.add(15.0). Keep the total line.

Starter code

Main.java
import java.util.ArrayList;

public class Main {
    public static void main(String[] args) {
        ArrayList<String> cart = new ArrayList<>();
        cart.add("Apple");
        cart.add("Bread");
        cart.set(0, "Apple x2");
        cart.remove(1);
        ArrayList<Double> prices = new ArrayList<>();
        prices.add(10.0);
        prices.add(20.0);
        double subtotal = 0;
        for (double price : prices) {
            subtotal += price;
        }
        double tax = subtotal * 0.10;
        double total = subtotal + tax;
        System.out.println(cart);
        System.out.println("Subtotal: " + subtotal);
        System.out.println("Total: " + total);
        // List every item one by one
    }
}

Sample solution

Main.java
import java.util.ArrayList;

public class Main {
    public static void main(String[] args) {
        ArrayList<String> cart = new ArrayList<>();
        cart.add("Apple");
        cart.add("Bread");
        cart.add("Milk");
        cart.set(0, "Apple x2");
        cart.remove(1);
        for (String item : cart) {
            System.out.println(item);
        }
        ArrayList<Double> prices = new ArrayList<>();
        prices.add(10.0);
        prices.add(20.0);
        prices.add(15.0);
        double subtotal = 0;
        for (double price : prices) {
            subtotal += price;
        }
        double tax = subtotal * 0.10;
        double total = subtotal + tax;
        System.out.println("Subtotal: " + subtotal);
        System.out.println("Total: " + total);
    }
}

Expected output

Apple x2
Milk
Subtotal: 45.0
Total: 49.5

Practice Full cart (3 items)

Add to the previous code: add a third item with cart.add("Milk"), update with cart.set(0, "Apple x2") and cart.remove(1). List all items with for (String item : cart) { System.out.println(item); }. Add a third price with prices.add(15.0). Print "Subtotal: " + subtotal and "Total: " + total with println.

Starter code

Main.java
import java.util.ArrayList;

public class Main {
    public static void main(String[] args) {
        ArrayList<String> cart = new ArrayList<>();
        cart.add("Apple");
        cart.add("Bread");
        cart.set(0, "Apple x2");
        cart.remove(1);
        ArrayList<Double> prices = new ArrayList<>();
        prices.add(10.0);
        prices.add(20.0);
        double subtotal = 0;
        for (double price : prices) {
            subtotal += price;
        }
        double tax = subtotal * 0.10;
        double total = subtotal + tax;
        System.out.println(cart);
        System.out.println("Subtotal: " + subtotal);
        System.out.println("Total: " + total);
        // List every item one by one
    }
}

Sample solution

Main.java
import java.util.ArrayList;

public class Main {
    public static void main(String[] args) {
        ArrayList<String> cart = new ArrayList<>();
        cart.add("Apple");
        cart.add("Bread");
        cart.add("Milk");
        cart.set(0, "Apple x2");
        cart.remove(1);
        for (String item : cart) {
            System.out.println(item);
        }
        ArrayList<Double> prices = new ArrayList<>();
        prices.add(10.0);
        prices.add(20.0);
        prices.add(15.0);
        double subtotal = 0;
        for (double price : prices) {
            subtotal += price;
        }
        double tax = subtotal * 0.10;
        double total = subtotal + tax;
        System.out.println("Subtotal: " + subtotal);
        System.out.println("Total: " + total);
    }
}

Expected output

Apple x2
Milk
Subtotal: 45.0
Total: 49.5

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What are the basic steps of the cart app?

  • Add, list, total Correct answer
  • Open, read, close
  • Print, wait, exit
  • Input, process, output

Explanation: The cart has adding, listing and total steps.

2 Match the cart pieces

Term Meaning
add Add an item
for-each List items
+= Addition
println Print

3 Complete the for-each

Question 
for (String item : ____) {
    System.out.println(item);
}
Answer 
for (String item : cart) {
    System.out.println(item);
}

Explanation: The cart variable is cart.

All lessons in Beginner

1 Java basics

  1. What is Java?
  2. The main method
  3. Comments
  4. Class skeleton
  5. javac and java
  6. Summary - Java basics

2 Variables

  1. int and double
  2. boolean
  3. String
  4. Naming variables
  5. final variables
  6. Summary - Variables

3 Data types

  1. Primitive types
  2. Type casting
  3. String concatenation
  4. Math class
  5. BigInteger and BigDecimal
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add/subtract
  3. Multiply/divide
  4. Error handling
  5. Putting it together

5 Operators

  1. Arithmetic
  2. Comparison
  3. Logical
  4. Bitwise
  5. Assignment and increment
  6. Summary - Operators

6 String basics

  1. length and charAt
  2. equals and equalsIgnoreCase
  3. indexOf and substring
  4. toUpperCase and trim
  5. String.format
  6. Summary - String basics

7 Conditionals

  1. The if statement
  2. else and else if
  3. Nested if
  4. switch
  5. Ternary
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. do-while
  4. break and continue
  5. for-each
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding items
  3. Calculating totals
  4. Updating quantity
  5. Putting it together

10 Arrays

  1. Declaring arrays
  2. Array access
  3. Filling arrays
  4. Multi-dimensional arrays
  5. Copying arrays
  6. Summary - Arrays

11 Array methods

  1. Arrays.sort
  2. Arrays.toString
  3. Arrays.binarySearch
  4. Arrays.copyOf
  5. Arrays.fill
  6. Summary - Array methods

12 Collections

  1. ArrayList
  2. add and get
  3. HashMap
  4. put and get
  5. HashSet
  6. Summary - Collections

13 Methods

  1. Defining methods
  2. return
  3. void methods
  4. Method overloading
  5. Scope
  6. Summary - Methods

14 Method parameters

  1. Primitive parameters
  2. Object parameters
  3. varargs
  4. Multiple values via array
  5. final parameters
  6. Summary - Method parameters

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 String builder

  1. StringBuilder
  2. append
  3. insert and delete
  4. reverse
  5. toString
  6. Summary - String builder

17 Input and output

  1. Scanner
  2. nextInt and nextLine
  3. System.out.printf
  4. BufferedReader
  5. try-with-resources
  6. Summary - Input and output

18 Enum

  1. Declaring enums
  2. values and valueOf
  3. Enum fields
  4. Enum methods
  5. switch with enum
  6. Summary - Enum

19 Exception basics

  1. try/catch
  2. finally
  3. throw
  4. Exception hierarchy
  5. Multiple catch
  6. Summary - Exception basics

20 Beginner final

  1. Project design
  2. Data model
  3. Business logic
  4. Error handling
  5. Putting it together