Java Basics

What is Java?

• A type of coffee

• A programming language

• A type of car

• An operating system

What are the main features of Java?

• Platform independence, object-oriented, robust standard library, automatic memory management

• Cross-platform compatibility, functional programming, extensive standard library, garbage collection

• Platform dependence, procedural programming, limited standard library, manual memory management

• Hardware dependence, structured programming, minimal standard library, manual memory allocation

Explain the difference between JDK, JRE, and JVM.

• JDK is the runtime environment for Java bytecode, JRE is used for Java development, and JVM is used for running Java applications

• JDK is used for running Java applications, JRE is the runtime environment for Java bytecode, and JVM is used for Java development

• JDK is used for JavaScript development, JRE is used for running JavaScript applications, and JVM is the runtime environment for JavaScript

• JDK is used for Java development, JRE is used for running Java applications, and JVM is the runtime environment where Java bytecode is executed.

What is the purpose of the 'static' keyword in Java?

• To define a variable or method that can be modified by any class

• To declare a variable or method that belongs to the class itself rather than to instances of the class.

• To allow multiple threads to access a method simultaneously

• To make a variable or method accessible only within the same package

What is the difference between '==' and '.equals()' in Java?

• '==' is used for comparing strings, '.equals()' is used for comparing integers

• '==' and '.equals()' are interchangeable in Java

• '==' compares reference, '.equals()' compares content

• '==' compares content, '.equals()' compares reference

What is inheritance in Java?

• A concept where classes can only inherit from interfaces

• A process of creating new classes from existing classes

• A feature that allows classes to share methods but not attributes

• A mechanism where a new class inherits properties and behaviors from an existing class.

What is polymorphism in Java?

• Polymorphism in Java is limited to working with objects of the same class only.

• Polymorphism in Java refers to the ability to use multiple inheritance.

• Polymorphism in Java allows methods to be written that can work with objects of different classes, providing flexibility and reusability in code.

• Polymorphism in Java is a feature that allows direct access to private methods of other classes.

Explain the concept of encapsulation in Java.

• Encapsulation in Java is the mechanism of wrapping the data (variables) and code acting on the data (methods) together as a single unit. It restricts direct access to some of the object's components, which helps in achieving data hiding and abstraction.

• Encapsulation in Java is a technique used to increase the speed of code execution.

• Encapsulation in Java involves exposing all object components for direct access.

• Encapsulation in Java refers to the process of compressing data files.

What are the different types of loops in Java?

• until loop

• for loop, while loop, do-while loop

• if loop

• repeat loop

What is the use of 'finally' block in Java?

• It is used to ensure that certain code is always executed, even if an exception is thrown.

• It is used to handle user input validation

• It is used to define new variables

• It is used to skip certain code execution