Merge pull request #40 from realpython/oop-in-java-vs-python

Add support files for OOP in Java vs Python article

Author: JFincher42

oop-in-java-vs-python/Car.java

@@ -0,0 +1,66 @@
+/**
+ * Car class
+ * 
+ * Used for the Real Python OOP in Java vs Python article
+ * 
+ * Requires both Vehicle.java and Device.java
+ */
+
+public class Car extends Vehicle implements Device {
+
+    private int year; // Year of our car
+    private int voltage; // Battery voltage
+    private static int wheels; // How many wheels do we have
+
+    /**
+     * Car constructor
+     */
+    public Car(String color, String model, int year) {
+        super(color, model);
+        this.year = year;
+        this.voltage = 12;
+    }
+
+    /**
+     * Override the interface method.
+     */
+    @Override
+    public int getVoltage() {
+        return voltage;
+    }
+
+    /**
+     * getYear returns the Car's year
+     */
+    public int getYear() {
+        return year;
+    }
+
+    /**
+     * setYear changes Car's year
+     */
+    public void setYear(int year) {
+        this.year = year;
+    }
+
+    /**
+     * getWheels returns the number of wheels
+     */
+    public static int getWheels() {
+        return wheels;
+    }
+
+    /**
+     * setWheels sets the number wheels
+     */
+    public static void setWheels(int count) {
+        wheels = count;
+    }
+
+    /**
+     * Return a human readable string reoresenting the Car
+     */
+    public String toString() {
+        return "Car: " + getColor() + " : " + getModel() + " : " + getYear();
+    }
+}

oop-in-java-vs-python/Device.java

@@ -0,0 +1,12 @@
+/**
+ * Device Interface
+ * 
+ * Used for the Real Python OOP in Java vs Python article
+ */
+public interface Device {
+
+    /**
+     * getVoltage returns the current battery voltage
+     */
+    int getVoltage();
+}

oop-in-java-vs-python/Vehicle.java

@@ -0,0 +1,48 @@
+/**
+ * Vehicle class
+ * 
+ * Used for the Real Python OOP in Java vs Python article
+ * 
+ * Implements basic functionality for our Vehicle
+ */
+public class Vehicle {
+
+    private String color; // What color are we?
+    private String model; // What model vehicle are we?
+
+    /**
+     * Vehicle constructor
+     */
+    public Vehicle(String color, String model) {
+        this.color = color;
+        this.model = model;
+    }
+
+    /**
+     * getColor returns the Vehicles color
+     */
+    public String getColor() {
+        return color;
+    }
+
+    /**
+     * setColor changes the Vehicles color
+     */
+    public void setColor(String color) {
+        this.color = color;
+    }
+
+    /**
+     * getModel returns the Vehicles model
+     */
+    public String getModel() {
+        return model;
+    }
+
+    /**
+     * setModel changes the Vehicles model
+     */
+    public void setModel(String model) {
+        this.model = model;
+    }
+}

oop-in-java-vs-python/car.py

@@ -0,0 +1,74 @@
+"""Car, Device, and Vehicle classes
+
+Used to demonstrate object oriented techniques in Java vs Python
+"""
+
+
+class Vehicle:
+    """The Vehicle class is the parent for all vehicles."""
+
+    def __init__(self, color, model):
+        """Define the color and model of our vehicle"""
+        self.color = color
+        self.model = model
+
+
+class Device:
+    """The Device class defines objects which have a battery."""
+
+    def __init__(self):
+        """Define the base voltage for our device."""
+        self._voltage = 12
+
+
+class Car(Vehicle, Device):
+    """The Car class is both a Vehicle and a Device."""
+
+    wheels = 0
+
+    def __init__(self, color, model, year):
+        """Call our parent classes, then define the year."""
+        Vehicle.__init__(self, color, model)
+        Device.__init__(self)
+        self.year = year
+
+    def add_wheels(self, wheels):
+        """Change the number of wheels we have."""
+        self.wheels = wheels
+
+    @property
+    def voltage(self):
+        """Allow us to access the Device._voltage property as voltage"""
+        return self._voltage
+
+    @voltage.setter
+    def voltage(self, volts):
+        """Warn the user before resetting the voltage"""
+        print("Warning: this can cause problems!")
+        self._voltage = volts
+
+    @voltage.deleter
+    def voltage(self):
+        """Warn the user before deleting the voltage"""
+        print("Warning: the radio will stop working!")
+        del self._voltage
+
+    def __str__(self):
+        """Improved human readable version of the object"""
+        return f"Car {self.color} : {self.model} : {self.year}"
+
+    def __eq__(self, other):
+        """Do these objects have the same year?"""
+        return self.year == other.year
+
+    def __lt__(self, other):
+        """Which object was made earlier than the other?"""
+        return self.year < other.year
+
+    def __add__(self, other):
+        """Add the objects together in our predefined way."""
+        return Car(
+            self.color + other.color,
+            self.model + other.model,
+            int(self.year) + int(other.year),
+        )