Can a class containing only abstract methods and no implementations be replaced with an interface?

Yes, if an abstract class contains only abstract methods and has no implementation, it can be replaced with an interface. In Java, an interface is specifically designed for declaring methods without implementation (up to Java 8), and serves to define a contract that classes must implement.

However, consider the following:

• An interface cannot contain state (fields), unlike an abstract class.
• From Java 8 onwards, interfaces can have methods with default implementations, but if you only have abstract methods, this does not affect your design.
• A class can implement multiple interfaces but can only inherit from one abstract class.

If your abstract class has no state and no implementations, an interface would be a more suitable and flexible solution.