java code flow

person/developer => Java code => compiler (Javac) => byte code => jvm (built different for each machines) => os ==> hw

jvm

• executes only public static void main (String a[])

java

• java is an oject oriented programming language
• object oriented programming languages means everything is an object

hello world in Java

class Hello {
    public static void main(String a[]){
        system.out.println("Hello world!");
    }
}

JVM

• jvm is part of jre(java runtime environment)

WORA (write once run anywhere)

• java is platform independent bcz of jvm , the other machine need only jvm and jre and no need for JDK to execute java code.

• jdk is needed by developer for development and jdk brings new/updated jre and jvm

java is strongly typed language

System.out.print

System.out.println() // ==> moves control to next line

String[] args in Java

In Java, String[] args is a parameter in the main method declaration. It is an array of strings that allows you to pass command-line arguments to your Java program when you run it from the command line. Let's break it down in detail:

String[] args

• String[]: This denotes that args is an array of strings. It means that you can store multiple strings in the args array.
• args: This is just a variable name. You can name it whatever you like, but args is a conventional name used in Java programs. It stands for "arguments".

Purpose and Importance

The String[] args parameter allows you to pass information to your Java program from the command line when you execute the program. This can be useful for various purposes, such as:

1. Configuration: You can pass configuration parameters to your program at runtime, such as file paths, database connection details, or other settings.

2. Customization: It allows users to customize the behavior of your program by providing arguments when they run it.

3. Input: You can pass input data to your program from the command line, which your program can then process.

4. Testing: It facilitates testing your program with different inputs without modifying the source code.

Example

Here's a simple example demonstrating how to use String[] args in a Java program:

public class CommandLineArgumentsExample {
    public static void main(String[] args) {
        // Printing all the command-line arguments passed to the program
        for (String arg : args) {
            System.out.println(arg);
        }
    }
}

• if you compile and run this program from the command line like this:

java CommandLineArgumentsExample arg1 arg2 arg3

• it will output:

arg1
arg2
arg3

conclusion

• In summary, String[] args in Java is a mechanism to pass command-line arguments to your program. While not strictly necessary for all programs, it is a convenient and powerful feature that allows your Java applications to be more flexible and customizable based on user input or configuration parameters provided at runtime.