10 Must know Java Full Stack Interview Questions With Answers

Java is called platform independent because of its byte codes which can run on any system irrespective of its underlying operating system.

Java is not 100% object-oriented because it includes primitive data types that are not objects and do not inherit from a common superclass. These data types have direct support from the language and are not encapsulated within classes. However, Java provides wrapper classes to allow primitive types to be used as objects when needed. This deviation from being purely object-oriented allows for better performance and memory efficiency in certain situations.

The most preferred language among Java Full Stack Developers is JavaScript. JavaScript is widely used for front-end web development, making it an essential skill for Java developers working on full-stack projects that involve both front-end and back-end development. Its popularity is due to its versatility, as it allows developers to create dynamic and interactive user interfaces, as well as server-side applications using Node.js. Java and JavaScript together provide a powerful combination for building robust and feature-rich web applications.

Wrapper classes in Java are classes that provide an object-oriented representation of primitive data types. They allow primitive values to be treated as objects, enabling Java developers to use object-oriented features with primitive data types. Examples of wrapper classes include Integer, Float, Character, and Boolean.

Callback Hell, also known as “pyramid of doom,” is a situation in asynchronous programming where multiple nested callbacks make the code difficult to read and maintain. It occurs when there are numerous dependent asynchronous operations that need to be executed sequentially or in a specific order. The excessive indentation and nesting of callbacks can lead to code that is hard to follow, debug, and refactor. This issue is commonly encountered in JavaScript and other languages with callback-based asynchronous programming, creating a challenging and error-prone development experience.

•  Final:
• Final is a keyword in Java that is used to declare a constant value or make a class, method, or variable unchangeable.
• When applied to a variable, it means the variable’s value cannot be modified once assigned.
• When applied to a method, it prevents the method from being overridden in subclasses.
• When applied to a class, it makes the class non-extendable, meaning no other class can inherit from it.

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• Finalize:
• Finalize is a method in the Object class that gets called by the garbage collector before reclaiming an object’s memory.
• Developers can override the finalize() method in their classes to perform cleanup tasks or release resources before an object is garbage-collected.
• However, it is generally recommended to use try-with-resources or other mechanisms to manage resources, as relying on finalize() for resource cleanup can be unpredictable and may lead to performance issues.

•  Finally:
• Finally is a block used in exception handling to ensure that certain code is executed, regardless of whether an exception occurs or not.
• It is typically used with try-catch blocks. The code within the finally block is executed after the try block finishes executing, regardless of whether an exception is thrown or caught.
• Finally is useful for releasing resources, closing files, or cleaning up operations that must be performed even in the presence of exceptions.

• Object-Oriented Programming (OOP):

OOP is a programming paradigm that revolves around objects, encapsulation, inheritance, and polymorphism. It focuses on organizing code into reusable and modular objects with attributes and methods.

• Functional Programming (FP):

FP is a programming paradigm that treats computation as the evaluation of mathematical functions. It emphasizes pure functions, immutability, and higher-order functions for concise and declarative coding.

Long Polling in Java is a web communication technique is where a client sends a request to the server, and the server holds the request open until new data is available or a timeout occurs. When the new data is available, the server responds to the client’s request with the updated data. This approach is used to implement real-time or near-real-time updates in Java web applications, allowing continuous updates without the need for constant polling.

 java.lang.Object is the root class for all Java classes, also inherited without explicit extension.

In Java, a class is a blueprint or template that defines the structure and behavior of objects. It encapsulates data and behavior related to the objects it represents, allowing developers to create multiple instances with similar properties and functionalities. Classes facilitate object-oriented programming principles like encapsulation, inheritance, and polymorphism.