How Java enabled High Performance?

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.

Variables defined inside methods, constructors or blocks are called local variables. The variable will be declared and initialized within the method and it will be destroyed when the method has completed.

In Java, a local variable is a variable that is defined within a method, constructor, or a block of code. It is only accessible within the block of code in which it is declared and cannot be accessed from outside that block. Local variables are created on the stack and their memory is automatically freed when the method, constructor, or block of code execution is completed.

Local variables have a scope that is limited to the method, constructor, or block of code in which they are declared. This means that they are only accessible within the block in which they are declared and cannot be accessed from outside that block. The lifetime of a local variable starts when the method, constructor, or block of code is entered and ends when it is exited.

Here is an example of a local variable in Java:

public void doSomething() {
   int i = 10;
   // Use the local variable i here.
}

In the example above, the local variable i is declared within the doSomething method and is only accessible within that method.

Instance variables are variables within a class but outside any method. These variables are instantiated when the class is loaded.

In Java, an instance variable is a variable that is declared within a class but outside of any method, constructor, or block of code. Unlike local variables, instance variables are associated with an instance of an object and are created when an object of the class is instantiated. This means that each object of the class will have its own copy of the instance variables, and changes to an instance variable in one object will not affect the value of the same instance variable in another object.

Instance variables have a default value, which is either null for reference types or 0 for numeric types. However, the default value can be overridden by assigning a value to the instance variable in the constructor or by using a setter method.

Instance variables are declared using the private access modifier to ensure that they cannot be accessed directly from outside the class. Instead, they are accessed using getter and setter methods.

Here is an example of an instance variable in Java:

public class Student {
   private int studentId;
   private String studentName;

   // Getter and setter methods for the instance variables
   public int getStudentId() {
      return studentId;
   }

   public void setStudentId(int studentId) {
      this.studentId = studentId;
   }

   public String getStudentName() {
      return studentName;
   }

   public void setStudentName(String studentName) {
      this.studentName = studentName;
   }
}

In the example above, the class Student has two instance variables studentId and studentName. Each object of the Student class will have its own copy of these instance variables, and their values can be accessed and modified using the getter and setter methods.

These are variables declared with in a class, outside any method, with the static keyword.

In Java, a class variable (also known as a static variable) is a variable that is declared with the "static" keyword and is associated with a class, rather than an instance of the class. This means that there is only one instance of the class variable shared among all objects of that class. The value of a class variable can be accessed using the class name and the dot operator (.) without creating an instance of the class. Class variables are used to store information that is common to all instances of a class, such as a constant value that is shared among all objects of a class.

Here's an example to illustrate the use of a class variable in Java:

class Circle {
   static final double PI = 3.14;
   double radius;
   double area;

   void setRadius(double r) {
      radius = r;
      area = PI * r * r;
   }
}

public class Main {
   public static void main(String[] args) {
      Circle circle1 = new Circle();
      Circle circle2 = new Circle();

      circle1.setRadius(5);
      circle2.setRadius(10);

      System.out.println("Circle1: " + circle1.area);
      System.out.println("Circle2: " + circle2.area);

      // Accessing the class variable using the class name and the dot operator
      System.out.println("PI: " + Circle.PI);
   }
}

In this example, the PI class variable is a constant value that is shared among all instances of the Circle class. The value of PI is accessed using the class name and the dot operator (.) in the setRadius method to calculate the area of the circle. The result of this program will be:

Circle1: 78.5
Circle2: 314.0
PI: 3.14