add methods for order and product class

add quantity class

src/main/java/seedu/address/model/order/Order.java

@@ -1,4 +1,73 @@
 package seedu.address.model.order;
 
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+
 public class Order {
+    private int id;
+    private Map<Product, Quantity> productMap;
+
+    public Order() {
+        productMap = new HashMap<>();
+    }
+
+    public Order(int id) {
+        this.id = id;
+        productMap = new HashMap<>();
+    }
+
+    public void setID(int id) {
+        this.id = id;
+    }
+
+    public Map<Product, Quantity> getProductMap() {
+        return this.productMap;
+    }
+
+    public void addProduct(Product newProduct, Quantity newQuantity) {
+        productMap.put(newProduct, newQuantity);
+    }
+
+    public Quantity getQuantity(Product product) {
+        Quantity currQuantity = productMap.get(product);
+        return currQuantity;
+    }
+
+    public int getQuantityValue(Product product) {
+        int value = productMap.get(product).getValue();
+        return value;
+    }
+
+    public void deleteProduct(Product product) {
+        productMap.remove(product);
+    }
+
+    public void clearOrder() {
+        this.productMap.clear();
+    }
+
+    @Override
+    public boolean equals(Object other) {
+        if (other == this) {
+            return true;
+        }
+        if (!(other instanceof Order)) {
+            return false;
+        }
+
+        Order otherOrder = (Order) other;
+        return (this.id == otherOrder.id)
+                && this.productMap.equals(otherOrder.productMap);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(id, productMap);
+    }
+
+    @Override
+    public String toString() {
+        return productMap.toString();
+    }
 }

src/main/java/seedu/address/model/order/Product.java

@@ -1,4 +1,50 @@
 package seedu.address.model.order;
 
 public class Product {
+
+    public static final String MESSAGE_CONSTRAINTS =
+            "Product names should only contain alphanumeric characters and spaces, and it should not be blank";
+
+    /*
+     * The first character of the product name must not be a whitespace,
+     * otherwise " " (a blank string) becomes a valid input.
+     */
+    public static final String VALIDATION_REGEX = "[\\p{Alnum}][\\p{Alnum} ]*";
+    private String name;
+
+    public Product(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public String toString() {
+        return this.name;
+    }
+
+    @Override
+    public boolean equals(Object other) {
+        if (other == this) {
+            return true;
+        }
+
+        if (!(other instanceof Product)){
+            return false;
+        }
+
+        Product otherProduct = (Product) other;
+        return this.name.equals(otherProduct.name);
+    }
+
+    @Override
+    public int hashCode() {
+        return this.name.hashCode();
+    }
+
+    public String getName() {
+        return this.name;
+    }
+
+    public void rename(String newName) {
+        this.name = newName;
+    }
 }

src/main/java/seedu/address/model/order/Quantity.java

@@ -0,0 +1,45 @@
+package seedu.address.model.order;
+
+public class Quantity {
+    public static final String MESSAGE_CONSTRAINTS =
+            "Product quantity should only be a number.";
+    public static final String VALIDATION_REGEX = "\\d";
+    public int value;
+
+    public Quantity(int value) {
+        this.value = value;
+    }
+
+    @Override
+    public String toString() {
+        return Integer.toString(this.value);
+    }
+
+    @Override
+    public boolean equals(Object other) {
+        if (other == this) {
+            return true;
+        }
+
+        // instanceof handles nulls
+        if (!(other instanceof Quantity)) {
+            return false;
+        }
+
+        Quantity otherQuantity = (Quantity) other;
+        return this.value == otherQuantity.value;
+    }
+
+    @Override
+    public int hashCode() {
+        return Integer.hashCode(this.value);
+    }
+
+    public int getValue() {
+        return this.value;
+    }
+
+    public void setQuantity(int newQuantity) {
+        this.value = newQuantity;
+    }
+}