Java Interview Question (Hard)

Constructors

• If no constructor is defined in a program, the compiler creates a default no-argument constructor.
• A constructor cannot be invoked without creating an object.
• A subclass does not inherit a constructor from its superclass.
• The key differences between constructors and methods are:
• Constructors do not have a return type, not even void.
• Constructors are called only once during object creation.
• Constructors have the same name as the class.

Java Platform

• The JVM (Java Virtual Machine) is responsible for executing Java bytecode on different platforms.
• Java is a platform-independent language because the JVM translates Java bytecode into machine-specific code.
• The 'overload' keyword is used to eliminate confusion between multiple methods of the same name.

Access Modifiers

• A class with the 'protected' access modifier is accessible within its class, its subclasses, and in the same package.

Inheritance

• Constructor chaining is the process of calling one constructor from another constructor in the same class or its superclass.
• Constructor chaining is achieved using the 'this' and 'super' keywords.
• Pointers are not supported in Java for security and memory management reasons.

Inheritance Examples

• A class inheriting from two classes is an example of multi-level inheritance.
• A class inheriting from a class that itself inherits from another class is an example of hierarchical inheritance.
• A combination of multi-level and hierarchical inheritance is an example of hybrid inheritance.
• A subclass providing a specific implementation of a method already provided by its superclass is an example of method overriding.

Methods and Variables

• A final method cannot be overridden in a subclass.
• An interface cannot be declared final in Java.
• Static binding in Java is a process where the method to be called is determined at compile-time.
• Dynamic binding in Java is a process where the method to be called is determined at runtime.
• The 'instanceof' operator checks if an object is an instance of a particular class or subclass.

Multithreading and Encapsulation

• A multithreaded program in Java is a program that can execute multiple threads concurrently.
• Encapsulation is a concept where an object's state is hidden from external interference and misuse.
• Abstraction in Java is the concept of showing only essential features of an object or system.
• Inheritance in Java is the process of creating a new class based on an existing class.
• Polymorphism in Java is the concept of an object taking on multiple forms.

Java Development Kits and Tools

• The JDK (Java Development Kit) is a software development kit that provides tools and libraries for Java development.
• The Javac compiler is used to compile Java source code into bytecode.
• Major features of Java include platform independence, object-oriented programming, and multithreading.
• The JDK includes the JRE (Java Runtime Environment) and development tools, whereas the JRE is a part of the JDK that provides a runtime environment for executing Java bytecode.

Test your knowledge on object-oriented programming concepts and keywords with this quiz. Explore topics such as inheritance, encapsulation, and the super keyword. Perfect for interview preparation or brushing up on your OOP skills.