Which statement is true about a class hierarchy in Java?

Which statement is true about a class hierarchy in Java?

• A. A class can extend multiple superclasses
• B. An interface cannot extend another interface
• C. A class can implement only one interface
• D. A class can extend one superclass and implement multiple interfaces

Answer: (D)

In Java, a class can extend one superclass and implement multiple interfaces. This single inheritance for classes keeps the hierarchy simple, while implementing interfaces lets a class gain multiple sets of behaviors from different sources. So a class can inherit fields and methods from one parent class and, at the same time, promise to provide the methods defined by any number of interfaces it implements. This is why the statement describing extending one superclass and implementing multiple interfaces is accurate. The other ideas don’t fit Java’s rules: a class cannot extend more than one superclass, so multiple inheritance of classes is not allowed. An interface can extend another interface, not only be limited to its own definition. And a class can implement more than one interface, not just a single one. Put together, the allowed combination described—extending a single superclass while implementing multiple interfaces—best captures how Java handles class hierarchies.

In Java, a class can extend one superclass and implement multiple interfaces. This single inheritance for classes keeps the hierarchy simple, while implementing interfaces lets a class gain multiple sets of behaviors from different sources. So a class can inherit fields and methods from one parent class and, at the same time, promise to provide the methods defined by any number of interfaces it implements. This is why the statement describing extending one superclass and implementing multiple interfaces is accurate.

The other ideas don’t fit Java’s rules: a class cannot extend more than one superclass, so multiple inheritance of classes is not allowed. An interface can extend another interface, not only be limited to its own definition. And a class can implement more than one interface, not just a single one. Put together, the allowed combination described—extending a single superclass while implementing multiple interfaces—best captures how Java handles class hierarchies.