Inheritance

There are two ways to handle object inheritance in Java: interfaces and abstract classes.

Abstract Classes

The easiest way is using abstract classes, but each class can inherit from a single abstract. On the other hand an abstract class can contain code.

Interfaces

Any class can inherit from many interfaces, but these contain no code. Instead they offer a common set of methods for the class.

It is recommended using an interface before an abstract class, as this will decouple code from more specific implementations.

Constants in Interfaces

Avoid adding constants to interfaces.

Interfaces and Testing

By using interfaces the code can be made easier to test, as implementations can be swapped with few problems.

Interfaces and Dependency Injection

In a similar way to testing, interfaces make it easier injecting dependencies, and swapping them.

Checking Inheritance

object instanceof ClassName

ClassName.class.isAssignableFrom(object)

More Information

• Interfaces and Inheritance