Java language was developed so that it does not depend on any hardware or software because the compiler compiles the code and then converts it to platform-independent byte code which can be run on multiple systems. The only condition to run that byte code is for the machine to have a runtime environment (JRE) installed in it.

It is not wrong if we claim that Java is the complete object-oriented programming language because everything in Java is under the classes and we can access them by creating the objects. But we can even say that Java is not a completely object-oriented programming language because it has the support of primitive data types like int, float, char, boolean, double, etc. Now for the question: Is Java a completely object-oriented programming language? We can say that - Java is not a pure object-oriented programming language, because it has direct access to primitive data types. And these primitive data types don't directly belong to the Integer classes.

C++ is only a compiled language, whereas Java is compiled as well as an interpreted language. Java programs are machine-independent whereas a c++ program can run only in the machine in which it is compiled. C++ allows users to use pointers in the program. Whereas java doesn’t allow it. Java internally uses pointers. C++ supports the concept of Multiple inheritances whereas Java doesn't support this. And it is due to avoiding the complexity of name ambiguity that causes the diamond problem.

Instance variables are those variables that are accessible by all the methods in the class. They are declared outside the methods and inside the class. These variables describe the properties of an object and remain bound to it at any cost. All the objects of the class will have their copy of the variables for utilization. If any modification is done on these variables, then only that instance will be impacted by it, and all other class instances continue to remain unaffected.
Local variables are those variables present within a block, function, or constructor and can be accessed only inside them. The utilization of the variable is restricted to the block scope. Whenever a local variable is declared inside a method, the other class methods don’t have any knowledge about the local variable.

• JVM : JVM also known as Java Virtual Machine is a part of JRE. JVM is a type of interpreter responsible for converting bytecode into machine-readable code. JVM itself is platform dependent but it interprets the bytecode which is the platform-independent reason why Java is platform-independent.
• JRE : JRE stands for Java Runtime Environment, it is an installation package that provides an environment to run the Java program or application on any machine.
• JDK : JDK stands for Java Development Kit which provides the environment to develop and execute Java programs. JDK is a package that includes two things Development Tools to provide an environment to develop your Java programs and, JRE to execute Java programs or applications.

Packages in Java can be defined as the grouping of related types of classes, interfaces, etc providing access to protection and namespace management.

Packages are used in Java in order to prevent naming conflicts, control access, and make searching/locating and usage of classes, interfaces, etc easier.

There are various advantages of defining packages in Java.

• Packages avoid name clashes.
• The Package provides easier access control.
• We can also have the hidden classes that are not visible outside and are used by the package.
• It is easier to locate the related classes.

There are two types of packages in Java

• User-defined packages
• Build In packages

There are 2 types of data types in Java as mentioned below:

• Primitive Data Type
• Non-Primitive Data Type or Object Data type

Primitive Data Type : Primitive data are single values with no special capabilities. There are 8 primitive data types:

• boolean : stores value true or false
• byte :stores an 8-bit signed two’s complement integer
• char : stores a single 16-bit Unicode character
• short : stores a 16-bit signed two’s complement integer
• int : stores a 32-bit signed two’s complement integer
• long : stores a 64-bit two’s complement integer
• float : stores a single-precision 32-bit IEEE 754 floating-point
• double : stores a double-precision 64-bit IEEE 754 floating-point

Non-Primitive Data Type: Reference Data types will contain a memory address of the variable’s values because it is not able to directly store the values in the memory. Types of Non-Primitive are mentioned below:

• Strings
• Array
• Class
• Object
• Interface

For doing operations on data, SQL has many built-in functions; they are categorized into two categories and further sub-categorized into seven different functions under each category. The categories are, Aggregate functions These functions are used to do operations from the values of the column, and a single value is returned.

• AVG()
• COUNT()
• FIRST()
• LAST()
• MAX()
• MIN()
• SUM()

• UCASE()
• LCASE()
• MID()
• LEN()
• ROUND()
• NOW()
• FORMAT()

• Inheritance
• Polymorphism
• Abstraction
• Encapsulation

• Public: The classes, methods, or variables which are defined as public, can be accessed by any class or method.
• Protected: The protected methods and members can be accessed by the class of the same package, by the sub-class of this class, or within the same class.
• Default: these methods and classes are accessible within the package only. By default, all the classes, methods, and variables are of default scope.
• Private: The private class, methods, or variables can be accessed within the class only.

Yes, It is possible to overload the main method. We can create as many overloaded main methods we want. However, JVM has a predefined calling method that JVM will only call the main method with the definition of -public static void main(string[] args)

You’ll find Java in the back end of websites and web apps, and it dominates the smartphone market as the primary language for Android development. It’s also used to process big data and build desktop, game, and cloud-based applications — and many companies use it to build their own internal tools and software.

While their names are similar, Java and JavaScript are two distinct languages. While versatile, JavaScript is primarily used in the web browser, whereas Java is commonly used for back-end development, scientific computing, and Android and IoT development.

Java is a high-level, object-oriented programming language known for its portability, security, and robustness. It's widely used in enterprise environments, mobile applications, and large systems development.

Begin with understanding Java basics like syntax, operators, data types, and control structures. Utilize online tutorials, books, and Java development environments for practice.

Key features include platform independence, object-oriented structure, strong memory management, high performance, and built-in security features.

Java is versatile for developing various types of applications including desktop applications, web applications, mobile apps (especially Android apps), and large-scale enterprise systems.