Java programming starting with Hello World

The JDK does not provide a separate editor. However, simple Java programs can be created with Notepad or an editing program.

The basic code for most programming languages is the code that prints the sentence “Hello World”. It is the most basic structure and relatively easy to understand.

The basic code for outputting Hello World in Java is shown below.

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

Java programs need to write code and then create a Java class file. The compile command is javac.

> javac HelloWorld.java

If you check the folder where javac command is executed, HelloWorld.class file is created. If you have a Java class file, you can run it with the java command.

> java HelloWorld

This program prints the characters “Hello, Java World” as shown below.

Creating a Hello World with a Java Applet

The applet program runs in the browser or applet viewer. Unlike Java applications, you need to add the required classes yourself.

The applet program that outputs Hello World is shown below.

import java.applet.*;
import java.awt.*;

public class HelloWorldApplet extends Applet {
	public void paint(Graphics g) {
		g.drawString("Hello, Java World", 100, 60);
	}
}
HelloWorldApplet.java

Java applets also need to create java class files like Java applications.

> javac HelloWorldApplet.java

When a class file named HelloWorldApplet.class is created, it creates an HTML file to run the applet.

<html>
<head>
	<title>Java Applet Test</title>
</head>
<body>
	<applet code="HelloWorldApplet.class" width="400" height="200"></applet>
</body>
</html>

The applet viewer is used as follows.

> appletviewer java_applet_test.html

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