- In the Java programming language, an interface is a reference type, similar to a class, that can contain only constants, method signatures, and nested types.
- Interfaces cannot be instantiated—they can only be implemented by classes or extended by other interfaces.
- To use an interface, you write a class that implements the interface. When an instantiable class implements an interface, it provides a method body for each of the methods declared in the interface.
- The Java programming language does not permit multiple inheritance.
- In Java, a class can inherit from only one class but it can implement more than one interface.