Source code - Guide to inheritance in Java

core-java/src/main/java/com/baeldung/inheritance/ArmoredCar.java

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+package com.baeldung.inheritance;
+
+public class ArmoredCar extends Car implements Floatable, Flyable{
+    private int bulletProofWindows;
+    private String model;
+    
+    public void remoteStartCar() {
+        // this vehicle can be started by using a remote control
+    }
+    
+    public String registerModel() {
+        return model;
+    }
+    
+    public String getAValue() {
+        return super.model;   // returns value of model defined in base class Car
+        // return this.model;   // will return value of model defined in ArmoredCar
+        // return model;   // will return value of model defined in ArmoredCar
+    }
+    
+    public static String msg() {
+    	// return super.msg(); // this won't compile.
+    	return "ArmoredCar"; 
+    }
+    
+	@Override
+    public void floatOnWater() {
+        System.out.println("I can float!");
+    }
+    
+	@Override
+    public void fly() {
+        System.out.println("I can fly!");
+    }
+    
+    public void aMethod() {
+        // System.out.println(duration); // Won't compile
+        System.out.println(Floatable.duration); // outputs 10
+        System.out.println(Flyable.duration); // outputs 20
+    }
+    
+    
+}

core-java/src/main/java/com/baeldung/inheritance/BMW.java

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+package com.baeldung.inheritance;
+
+public class BMW extends Car {
+    public BMW() {
+    	super(5, "BMW");
+    }
+	
+	@Override
+    public String toString() {
+    	return model;
+    }
+}

core-java/src/main/java/com/baeldung/inheritance/Car.java

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+package com.baeldung.inheritance;
+
+public class Car {
+	private final int DEFAULT_WHEEL_COUNT = 5;
+	private final String DEFAULT_MODEL = "Basic";
+
+	protected int wheels;
+    protected String model;
+    
+    public Car() {
+    	this.wheels = DEFAULT_WHEEL_COUNT;
+    	this.model = DEFAULT_MODEL;
+    }
+    
+    public Car(int wheels, String model) {
+    	this.wheels = wheels;
+    	this.model = model;
+    }
+        
+    public void start() {
+        // Check essential parts
+        // If okay, start.
+    }
+    public static int count = 10;
+    public static String msg() {
+        return "Car";
+    }
+    
+    public String toString() {
+    	return model;
+    } 
+}

core-java/src/main/java/com/baeldung/inheritance/Employee.java

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+package com.baeldung.inheritance;
+
+public class Employee {
+    private String name;
+    private Car car;
+    
+    public Employee(String name, Car car) {
+        this.name = name;
+        this.car = car;
+    }
+    
+    public Car getCar() {
+    	return car;
+    }
+}

core-java/src/main/java/com/baeldung/inheritance/Floatable.java

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+package com.baeldung.inheritance;
+
+public interface Floatable {
+    int duration = 10;
+    void floatOnWater();
+    
+    default void repair() {
+        System.out.println("Repairing Floatable object");   
+    }
+}

core-java/src/main/java/com/baeldung/inheritance/Flyable.java

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+package com.baeldung.inheritance;
+
+public interface Flyable {
+    int duration = 10;
+    void fly();
+    
+    /*
+     * Commented 
+     */
+    //default void repair() {
+    //    System.out.println("Repairing Flyable object"); 
+    //}
+}

core-java/src/main/java/com/baeldung/inheritance/SpaceCar.java

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+package com.baeldung.inheritance;
+
+public class SpaceCar extends Car implements SpaceTraveller {
+	@Override
+    public void floatOnWater() {
+        System.out.println("SpaceCar floating!");
+    }
+    
+	@Override
+    public void fly() {
+        System.out.println("SpaceCar flying!");
+    }
+    
+	@Override
+    public void remoteControl() {
+        System.out.println("SpaceCar being controlled remotely!");
+    }
+}

core-java/src/main/java/com/baeldung/inheritance/SpaceTraveller.java

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+package com.baeldung.inheritance;
+
+public interface SpaceTraveller extends Floatable, Flyable {
+    int duration = 10;
+    void remoteControl();
+}