Java FAQ: Top Questions

An interface in Java is a blueprint of a class, defining method signatures (and constants) that implementing classes must provide. It supports abstraction and multiple inheritance.

• Declaration: Defined with the interface keyword.
• Implementation: Classes implement interfaces using the implements keyword.
• Methods: Before Java 8, interfaces had only abstract methods (no body). Since Java 8, they can include default and static methods with implementations.
• Multiple Inheritance: A class can implement multiple interfaces, unlike extending multiple classes.
• Use Case: Defines contracts for classes (e.g., Comparable , Serializable ).