public static Priced mostExpensive(ArrayList<Priced> list) {...}

Week 6: Methods of OO Programming/10A. Interface Class as Variable Type+++

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+Although an object cannot be formed from an interface, an 'interface' can be used as a 'variable type'. 
+Such a variable can store a REFERENCE to 'ANY OBJECT THAT IMPLEMENTS the INTERFACE'. 
+However, note that ONLY OPERATIONS defined IN the INTERFACE can be called through such a variable.
+
+
+Let’s examine a method named ‘mostExpensive’, which takes a list of ‘Priced’ type objects as a parameter. 
+The method finds the most expensive among these.
+
+Below is a refresher on the interface class ‘Priced’:
+
+interface Priced {
+    int givePrice();
+}
+
+
+
+
+ 
+
+The static method 'mostExpensive' now returns the element with the highest price from the given elements:
+
+public static Priced mostExpensive(ArrayList<Priced> list) {
+
+    Priced mostExpensive = list.get(0);
+    for (Priced product : list) {
+
+        // 'product' object is from a class implementing the 'Priced' interface
+        // which can use the 'givePrice' method from the interface
+        if (product.givePrice() > mostExpensive.givePrice()) {
+            mostExpensive = product;
+        }
+    }
+    return mostExpensive;
+}
+ 
+
+
+
+
+
+
+
+The objects in the list can be of different types, the only REQUIREMENT is that EACH IMPLEMENTS the "Priced" interface.
+Examples include the classes "Fruit", "Car" and "MovieTicket":
+
+class Fruit implements Priced {
+    private String name;
+    
+    public Fruit(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public int givePrice() {
+        return 10;
+    }
+}
+
+
+
+class Car implements Priced {
+    private String brand;
+    private int price;
+    
+    public Car(String brand, int price) {
+        this.brand = brand;
+        this.price = price;
+    }
+
+    @Override
+    public int givePrice() {
+        return price;
+    }
+}
+
+
+
+class MovieTicket implements Priced {
+    private String movie;
+    private int ageLimit;
+    private int price;
+    
+    public MovieTicket(String movie, int ageLimit, int price) {
+        this.movie = movie;
+        this.ageLimit = ageLimit;
+        this.price = price;
+    }
+
+    @Override
+    public int givePrice() {
+        return price;
+    }  
+}
+
+
+
+
+
+Let's create a few objects and call the method:
+public static void main(String[] args) {
+    ArrayList<Priced> products = new ArrayList<>();
+    products.add(new Car("Mercedes", 15000));
+    products.add(new MovieTicket("Rambo 6", 21, 13));
+    products.add(new Fruit("Banana"));
+    
+    Priced mostExpensive = mostExpensive(products);
+}
+
+