What is the base class of all Java classes?

• A. java.lang.Class
• B. java.lang.Object
• C. java.lang.Base
• D. java.lang.System

Answer: (B)

In Java, every class that you create implicitly extends the java.lang.Object class if it does not explicitly extend another class. This means that java.lang.Object serves as the ultimate parent class for all Java classes. It provides fundamental methods like equals(), hashCode(), toString(), and methods for synchronization, among others, which become available to every class.

This design allows for a consistent interface for objects, promoting polymorphism — any object of a derived class can be treated as an object of the base class. For instance, if you have a class Dog that extends Animal, and both Dog and Animal ultimately inherit from Object, you can store references of both types in a variable of type Object.

The presence of the Object class as the root class ensures that certain capabilities and behaviors are uniformly available across all classes in Java, simplifying programming and fostering code reusability. Other classes listed, such as java.lang.Class, do not serve as base classes for user-defined classes, while java.lang.System provides utility functionalities and java.lang.Base is not a standard Java class.