Abstract classes and interfaces in Java serve fundamentally different purposes. Learn the differences between these Java language elements and how to use them in your programs. Abstract classes ...

Interfaces, however, support multiple inheritances where abstract classes don't. Implementation is done similarly in Java. For example, using the keyword implements will make a Java interface, while ...

Library authors would prefer to use interfaces to expose opaque abstractions; abstract classes were meant to be an implementation aid, not a modeling tool. (See Effective Java, "Prefer interfaces ...