Add JavaDoc to the Item class.

src/main/java/no/ntnu/idatt1002/demo/data/Item.java

 package no.ntnu.idatt1002.demo.data;
 
+/**
+ * The Item class represents an object or service purchased in real life. The item belongs to a category and
+ * has a price and description. The description may be left blank, but the Item must belong to a category and must
+ * have a price.
+ * @author HanneSofie
+ *
+ */
 public class Item {
-
     private Category category;
     private String description = "";
     private float price;
 
+    /**
+     * The constructor of a new Item object takes in a Category and a price. The category is a value of the
+     * Category enum class, whereas the price is provided as a float. If category or price is left blank, an
+     * IllegalArgumentException is thrown.
+     * @param category The category the Item belongs to.
+     * @param price The price of an Item as a float.
+     */
     public Item (Category category, float price){
         if(category == null || price <= 1.0f) {
             throw new IllegalArgumentException("The item must have a category and a price.");
@@ -15,33 +28,66 @@ public class Item {
         }
     }
 
+    /**
+     * The constructor instantiates a new Item object with a category, a description and a price as arguments. It
+     * overloads the first constructor to set the category and price and then sets the description of the item.
+     * If either 0category or price is left blank, an IllegalArgumentException is thrown.
+     * @param category The category the Item belongs to.
+     * @param description A description of the item as a String.
+     * @param price The price of the item as a float.
+     */
     public Item (Category category, String description, float price){
        this(category, price);
        this.description=description;
     }
 
-
-
+    /**
+     * The method returns the category to which the Item belongs as a value of the Category enum class.
+     * @return The category the Item belongs to as a value of the Category enum class.
+     */
     public Category getCategory() {
         return category;
     }
 
+    /**
+     * The method sets the category of an item to a value of the Category enum class.
+     * @param category The category to which the Item should belong.
+     */
     public void setCategory(Category category) {
+        if(category == null) {
+            throw new IllegalArgumentException("The category must be valid.");
+        }
         this.category = category;
     }
 
+    /**
+     * The method returns the description of the given Item object as a String.
+     * @return The description of the Item as a String.
+     */
     public String getDescription() {
         return description;
     }
 
+    /**
+     * The method sets the description of the Item object equal to the passed String. The String may be empty.
+     * @param description The new description of the Item object as a String.
+     */
     public void setDescription(String description) {
         this.description = description;
     }
 
+    /**
+     * The method returns the price of the given Item object as a float.
+     * @return The price of the Item as a float.
+     */
     public float getPrice() {
         return price;
     }
 
+    /**
+     * The method changes the price of the given Item to the passed price as a float.
+     * @param price The new price of the Item as a float.
+     */
     public void setPrice(float price) {
         this.price = price;
     }