First Program And the main() method

In this chapter, we will Write our first Java program and understand the basic structure of the main method.

Example:

package quipohouse;
public class FirstProgram
{
   public static void main(String[] args)
    {
      System.out.println("Welcome TO Quipo House");
    }
}

Output:-

Welcome TO Quipo House

main() Method

The main() method is a predefined method in Java. The JVM starts compiling the program from the main method.
We can Overload the main method also.
It always be public because JVM needs to access the file for compiling the program.
The keyword static is used because of memory management and JVM does not need to create an object to execute the main method.
The return type of the main method is void because it doesn't return any value or data after execution.
The String [ ] args is used to pass the input into the main method as arguments or parameters. " String [ ] " is called a string array means a group of arrays. Users can insert a string array as input through the command line.

Explanation of main method declaration:

Explanation of print statement:

The System.out.println(); is used to print the output in the console.

How to Create and execute a Java program

Step-0: Open the notepad.

Step 1: Write the program.

Step 2: Click on the file then click on save.

Step-3: Save the file with Class Name and with Java extension.

Select file type (All Files).

Step-4: Now copy the path of the folder where you create the Java file

Step-5: Open Command Prompt or Just Press WIN+ R It opens run and then type cmd and hit enter.

The Command Prompt will pop up.

Step-6: Type the command cd and hit enter.

Step-7: Now type cd with path (i.e. cd documents than subfolder java).

Step-8: The class file of the java file is now displayed in the folder where you saved your java file.

Step-9: Now type javac and Java file with the extension

Step-10: Now just type the java and the file name and then hit enter.

You have successfully executed your first Java program.

What will happen if we try to run a Java program without a main method?

For example, try to write this program and run it just like the above procedure:

public class MyClass {
  // This is not a main method
  public static void myMethod() {
    System.out.println("Welcome to Quipo Tutorials!");
  }
}

After running the code by using the command java we will get the following output:

Two-min Drills

Creating a New File: First of all, open IDE and create a new project, and add a new Java class file. For example, HelloWorld.java.

Write the Code: Add the basic code structure with the main method:

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

Compilation of Program: Save and compile the code using any integrated environment or from the command prompt using the command javac HelloWorld.java.
Run the Program: Run the program to show the output, "Hello, World!", and by doing so, make sure everything is running correctly.