How are instance variables initialized in Java?

• A. They must be initialized before use
• B. They are automatically assigned default values
• C. They are not allowed in Java classes
• D. They must be declared static

Answer: (B)

Instance variables in Java are automatically assigned default values if they are not explicitly initialized. When an object of a class is created, each instance variable is given a default value based on its data type. For instance, numeric types (like int, float, etc.) are initialized to 0, the boolean type defaults to false, and reference types (like objects) are initialized to null. This automatic assignment facilitates programming since developers don’t need to initialize instance variables manually before using them—unless a specific non-default value is desired.

This behavior is fundamental to Java's design, supporting both safety and ease of use by preventing potential issues associated with using uninitialized variables. Hence, when instance variables are created as part of an object, the Java runtime system takes care of initializing them to their respective default values. This ensures that they have a known state right from the time an instance of the class is created.