Final answer:
In Java, interfaces allow for abstraction by defining method signatures without implementation and can provide multiple inheritance of type. Classes implementing interfaces must define all of its methods, promoting a flexible application structure.
Step-by-step explanation:
Abstraction using Interfaces in Java
Abstraction in Java can be achieved using interfaces. An interface in Java is a reference type, similar to a class, that can contain only constants, method signatures, default methods, static methods, and nested types. Method bodies exist only for default methods and static methods. Interfaces cannot be instantiated—they can only be implemented by classes or extended by other interfaces. One of the key advantages of using interfaces is that they allow for multiple inheritance of type, which means a class can implement multiple interfaces. This is in contrast to abstract classes as Java does not support multiple inheritances of state.
When a class implements an interface, it must provide implementations for all of the methods declared by the interface. This aspect of interfaces is essential for abstraction, as it allows for the separation of the definition of methods from their implementation.
The use of interfaces enables a flexible structure that can support the evolution of an application without compromising the entire architecture. Other than defining abstract methods, interfaces can also provide a way to define common constants that can be used across multiple classes.