Java Basics : MCQs & PYQs with Explanation

Option C

Java is widely used for Internet and web-based applications because of several important features. One of the key requirements for Internet applications is that programs must run on different platforms without modification and support networked or distributed computing.
Java fulfills these requirements through its Portability, meaning compiled Java bytecode can run on any system with a Java Virtual Machine (JVM), and its ability to work in a Distributed environment, allowing objects and programs to communicate over networks.

Option D

The Java Development Kit (JDK) is a software development kit provided by Java to help programmers develop Java applications. It contains tools for writing, compiling, and running Java programs. 
The JDK includes the Java Compiler (javac) to convert source code into bytecode, the Java Runtime Environment (JRE) to execute Java programs, and other development tools such as debuggers and documentation generators.

Option C

Java is a widely used Object-Oriented Programming (OOP) language that supports core OOP principles such as classes, objects, inheritance, polymorphism, abstraction, and encapsulation.

• PROLOG is a logic programming language.
• C Language is a procedural programming language.
• COBOL is a procedural and business-oriented language.

Option D

In Java, access modifiers determine the visibility of class members. The two commonly used modifiers are public and private.
Private members are accessible only within the same class in which they are declared, they cannot be accessed from subclasses or other classes.
Public members are accessible from any other class, regardless of the package or subclass relationship.

MEMBER ACCESS RULE TABLE:

Option A

While Java as a language is platform-independent, the Java Virtual Machine (JVM) itself is hardware and platform dependent.
Every operating system (Windows, Linux, MacOS) and hardware architecture (x86, ARM) requires its own specific implementation of the JVM to bridge the gap between Java's bytecode and the host's native environment.

Option C

In Java, access modifiers like public, protected, and private cannot be used for local variables inside a method. These modifiers are only allowed for class-level variables (instance or static variables), not inside the main() method.

Option A

Command Line Argument are parameters that are supplied to the application program at the time of invoking it for execution. We can customize the behavior of the main() method using command-line arguments.
When command line arguments are supplied to JVM, JVM wraps these and supply to args[ ]. It can be confirmed that they are actually wrapped up in args array by checking the length of args using args.length.

• In C and C++, the first command line argument is the file name whereas in Java the first command line argument is the first actual argument and not the file name.
• In Java, all command line arguments are object of String class.

For the command java cmd a b c d the arguments are assigned as follows:

• args[0] = "a"
• args[1] = "b"
• args[2] = "c"
• args[3] = "d"

The statement System.out.println(args[2]); will print the value stored at index 2, which is "c".

Option D

Compilation : Converting the Java source code (.java file) into bytecode (.class file) that can run on the Java Virtual Machine (JVM). The javac command is used to compile Java source code into bytecode.
javac FirstExample.java
Execution : Running the bytecode on the JVM. The java command is used to run the bytecode on the JVM.
java FirstExample

Option D

Java is a platform-independent programming language, which means Java programs can run on any operating system without modification. This is possible because Java does not compile code directly into machine-specific instructions. 
Instead, Java source code (.java files) is first compiled by the Java Compiler into an intermediate form called bytecode (.class files). Bytecode is platform-independent and cannot be executed directly by the operating system. To run a Java program, the Java Virtual Machine (JVM) is used.
The JVM is a part of the Java Runtime Environment (JRE), and it is responsible for interpreting or converting the bytecode into machine-specific code that the operating system can execute.

Option C

In Java, when you compile a .java file using the javac compiler, it does not directly generate machine code. Instead, it produces an intermediate code known as bytecode, stored in .class files. 
This bytecode is platform-independent, meaning it can run on any device that has the Java Virtual Machine (JVM). The JVM then converts this bytecode into machine-specific instructions depending on the operating system and hardware. This is the main reason Java is called Write Once, Run Anywhere (WORA).

Option D

Java programs are compiled into bytecode, which is an intermediate, platform-independent code. This bytecode is executed by the Java Virtual Machine (JVM), which interprets [Just-In-Time (JIT)] compiles it for the underlying hardware. The advantages of Java bytecode include:

• Portability : The same bytecode can run on any system with a compatible JVM.
• Platform Independence : Programs are not tied to a specific operating system or hardware.
• Security : The JVM provides a controlled environment, reducing risks like memory corruption.

However, bytecode is generally slower than native machine code because it must be interpreted or compiled at runtime.

Option D

In Java, access modifiers are keywords used to define the visibility and accessibility of classes, methods, and variables. They control which parts of a program can access a particular class member. Java provides four main access levels, public, private, protected, and the default (no modifier).
The public modifier allows access from anywhere, private restricts access to within the same class, and protected allows access within the same package and subclasses.

Option B

The Java Virtual Machine (JVM) is responsible for running compiled Java programs, but it does not compile the source code itself. The compilation of .java files into .class bytecode is done by the Java compiler (javac), not by the JVM.
Once Java bytecode exists, the JVM mainly performs three related class‑handling steps, Loading, Linking, and Initialization.
Loading: The JVM loads class files (bytecode) into memory by reading them from the file system, network, or other sources.
Linking: The loaded class is linked with already‑loaded classes (symbolic references are resolved, verification may happen).
Initialization: Static variables are set to their initial values and static blocks are executed.
Therefore, among the given options, Loading is the most appropriate single answer.

Option C

In Java programming, the Java source code (.java) is first compiled by the Java Compiler into Byte Code (.class). Byte Code is a standardized machine-independent code that can be executed on any platform using the Java Virtual Machine (JVM).