The Object Class

So far, the examples have shown classes defined independently. In Java, every class participates in a common inheritance hierarchy. Every class implicitly extends java.lang.Object, the root of the class hierarchy. As a result, even an empty class inherits the default behavior defined in Object.

By default, these implementations are generic. Objects are represented as a class name followed by a hash code, and equality is based on reference identity rather than object state. To define meaningful domain types, these methods should be overridden to control string representation and equality semantics.

The universal superclass

The Object class sits at the very top of Java’s inheritance tree. When we define a class without using the extends keyword, the Java compiler automatically adds extends Object for us.

If we write:

The compiler treats it as:

This means every reference type in Java:

• Inherits methods from Object

• Can be treated polymorphically as an Object

• Shares a common behavioral baseline

This mechanism ensures that every object in Java shares a common set of methods, allowing generic ...