Suppose you write a program for computing the perimeter of a rectangle and you mistakenly write your program so that it computes the area of a rectangle. What kind of error is this?

1 public class Welcome {
2 public void Main(String[] args) {
3 System.out.println('Welcome to Java!);
4 }
5 }

Line 2. Main should be main. 
Line 2. static is missing.
Line 3: Welcome to Java! should be enclosed inside double quotation marks.
Line 5: The last ) should be }. 

1 public static void main(String[] args) {
2 }
3 public class Welcome {
4 System.out.println("afternoon");
5 System.out.println("morning");
6 } 

public class Welcome {
  public static void main(String[] args) {
    System.out.println("morning");
    System.out.println("afternoon");
  }
}

Java is a high-level programming language originally developed by Sun Microsystems and released in 1995. Java runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX.

Some features include Object Oriented, Platform Independent, Robust, Interpreted, Multi-threaded

1. Object-Oriented: Java is an object-oriented programming language, which means it is based on the concept of objects and classes.

2. Platform Independent: Java code can run on any device or operating system with a Java Virtual Machine (JVM) installed, making it a "write once, run anywhere" language.

3. Memory Management: Java has a built-in automatic memory management system, freeing the programmer from having to manually allocate and deallocate memory.

4. Security: Java has strong security features that help protect against malicious attacks and unauthorized access to sensitive data.

5. Large Standard Library: Java has a large standard library that provides pre-written code for common tasks, reducing the need to write code from scratch and speeding up the development process.

Java is considered to be architecturally neutral because it was designed to be platform-independent. This means that Java code can be compiled on one platform and executed on another platform without modification.

Java achieves platform-independence by using a "compile once, run anywhere" approach. Java code is compiled into bytecode, which is a platform-independent code format that can be executed on any platform that has a Java Virtual Machine (JVM) installed. The JVM interprets the bytecode and executes the Java program.

By using bytecode and a JVM, Java is able to abstract away the underlying platform-specific details and provide a consistent, reliable runtime environment for Java programs. This makes Java well-suited for distributed computing environments, where different systems and architectures may be used.

In summary, Java is architecturally neutral because it separates the code from the underlying platform by using bytecode and a JVM, allowing Java programs to be executed on any platform that supports Java.

Java uses Just-In-Time compiler to enable high performance. Just-In-Time compiler is a program that turns Java bytecode, which is a program that contains instructions that must be interpreted into instructions that can be sent directly to the processor.

Java provides several features that enable high performance, including:

1. Just-In-Time (JIT) compilation - Java uses a JIT compiler to improve the performance of the code at runtime. The JIT compiler compiles the bytecode to native machine code, optimizing it for the specific hardware and operating system on which it is running. This approach allows Java to achieve performance similar to that of native code while still maintaining the benefits of platform independence.

2. Garbage collection - Java's automatic garbage collection feature allows it to manage memory usage efficiently. This means that Java programs can avoid common memory-related errors such as memory leaks, resulting in more stable and reliable performance.

3. Multithreading support - Java provides built-in support for multithreading, allowing programs to run multiple threads of execution simultaneously. This feature enables Java programs to take advantage of modern multi-core CPUs, improving performance on multi-threaded applications.

4. Platform independence - Java's platform independence allows it to run on a variety of hardware and operating systems. This means that Java programs can be optimized for the specific hardware and operating system on which they are running, leading to better performance.

5. Bytecode format - Java's bytecode format is highly optimized, allowing for efficient execution and minimizing the overhead of interpretation. This approach allows Java to achieve good performance even on systems with limited resources.

Overall, Java's combination of JIT compilation, garbage collection, multithreading support, platform independence, and optimized bytecode format enables it to deliver high performance, making it a popular choice for building high-performance applications.

Java is considered a dynamic language for several reasons:

1. Late binding - Java uses late binding, also known as dynamic binding, which means that the determination of which method to call happens at runtime, rather than at compile time. This allows for more flexibility and adaptability in program execution, as the method to be called can be determined based on the state of the program at runtime.

2. Reflection - Java has a built-in reflection API that allows the program to examine and modify itself at runtime. This feature enables dynamic loading of classes, invocation of methods by name, and inspection of class metadata at runtime.

3. Dynamic class loading - Java allows classes to be loaded at runtime, rather than at compile time. This feature enables the program to dynamically load and unload classes based on runtime conditions, providing greater flexibility in program execution.

4. Dynamic memory allocation - Java uses dynamic memory allocation, allowing the program to allocate and deallocate memory at runtime as needed. This feature enables more efficient memory management and better resource utilization.

5. Dynamic code execution - Java provides a built-in scripting engine, allowing for the execution of dynamic code at runtime. This feature enables the program to execute code that is generated or modified during runtime, providing greater flexibility in program execution.

In summary, Java is considered a dynamic language due to its support for late binding, reflection, dynamic class loading, dynamic memory allocation, and dynamic code execution. These features enable Java programs to be more flexible, adaptable, and efficient, making it a popular choice for building dynamic, high-performance applications.

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Dear readers, these Java Interview Questions have been designed especially to get you acquainted with the nature of questions you may encounter during your interview for the subject of Java Programming Language. As per my experience, good interviewers hardly planned to ask any particular question during your interview, normally questions start with some basic concept of the subject and later they continue based on further discussion and what you answer ?

What do you know about Java?
Java is a high-level programming language originally developed by Sun Microsystems and released in 1995. Java runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX.

What are the supported platforms by Java Programming Language?
Java runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX/Linux like HP-Unix, Sun Solaris, Redhat Linux, Ubuntu, CentOS, etc.

List any five features of Java?
Some features include Object Oriented, Platform Independent, Robust, Interpreted, Multi-threaded

Why is Java Architectural Neutral?
It’s compiler generates an architecture-neutral object file format, which makes the compiled code to be executable on many processors, with the presence of Java runtime system.

How Java enabled High Performance?
Java uses Just-In-Time compiler to enable high performance. Just-In-Time compiler is a program that turns Java bytecode, which is a program that contains instructions that must be interpreted into instructions that can be sent directly to the processor.

Why Java is considered dynamic?
It is designed to adapt to an evolving environment. Java programs can carry extensive amount of run-time information that can be used to verify and resolve accesses to objects on run-time.