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:
- 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.