Internal Details of Hello Java Program

The "Hello Java" program is a simple Java program that displays the message "Hello, World!" on the console. Here is the source code:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

Let's break down the code and discuss some of its internal details:

• public class HelloWorld: This line declares a public class called HelloWorld. In Java, every program must have at least one class with a main() method, which is the entry point of the program.

• public static void main(String[] args): This line declares the main() method, which is the starting point of the program. It is a public, static, void method that takes an array of Strings as its argument.

• System.out.println("Hello, World!");: This line prints the message "Hello, World!" to the console. The System.out.println() method is a built-in Java method that prints a message to the console and adds a newline character at the end.

Overall, the "Hello Java" program is a very basic program that demonstrates how to print a message to the console using Java.

What happens at runtime of Java Program ?

 t runtime, a Java program goes through several stages of execution. Here is a brief overview of what happens at runtime of a Java program:

1. Compilation: Before a Java program can be executed, it must first be compiled into bytecode. This is done by the Java compiler, which takes the source code and compiles it into a format that can be understood by the Java Virtual Machine (JVM).

2. Loading: Once the bytecode is generated, it needs to be loaded into memory. This is done by the class loader, which loads the bytecode of each class as it is needed.

3. Linking: After the classes have been loaded into memory, the JVM performs linking, which involves verifying and preparing the classes for execution. This includes verifying that the bytecode is valid, resolving any external references, and allocating memory for class variables and other resources.

4. Initialization: Once the classes have been linked, the JVM initializes them by setting the default values for any class variables and calling the static initializer block (if one exists).

5. Execution: Once the classes have been initialized, the main method is called, and the program begins to execute. During execution, the JVM interprets the bytecode and executes the instructions as they are encountered. As the program runs, it may allocate and deallocate memory as needed, interact with the operating system, and communicate with other programs or devices.

6. Termination: When the program has finished executing, it terminates. This may happen naturally when the main method returns, or it may be forced by calling System.exit(). When the program terminates, any allocated memory is freed, and the resources used by the program are released back to the operating system.