Applets in Java

In Java, developers can use the applet concept to seamlessly combine web browsers and pages, resulting in a specific output. Applets in Java can range from a simple applet to a very complex one. A simple Hello World applet lets someone see how a basic Java applet works and can be represented on the screen. In this article, we will explore the basic Java applets and another Java applet that finds extensive usage in solving various real-life problems. Java applets can be implemented into several other programming languages, such as Python, Dot Net, and other codes.

The Lifecycle of Applets in Java

In this phase, we will observe the applet’s lifecycle.

Start Your Free Software Development Course

Web development, programming languages, Software testing & others

There are five basic phases for the lifecycle of an applet.

1. Initialize
2. Started
3. Painted
4. Stopped
5. Destroyed

Let us see what these 5 phases do:

• The applet achieves its initialization, including the setup of all the necessary variables for execution, by utilizing the init() function.
• The applet is started. After completing the initialization step, the applet uses the start() function to begin its execution and move on.
• The paint() method is in charge of creating and carrying out the applet’s fundamental functionality while the applet goes through the painting process.
• The applet is stopped.
• The applet is destroy() function is responsible for removing all contents from the main memory, indicating the removal process.

Working on Applets in Java

Whenever an applet runs, it sequentially calls several functions to determine the main objective and generate multiple outputs.

The applet sequentially calls the following functions:

• Init()= The init () is a function called at the beginning of the program to assign different variables to the program and implement them in real-time.
• Start()– The Start () is usually called after the init (), and it is called to see the HTML screen that is present along with the Java coding. Whenever a user leaves an open HTML Screen and returns, he goes from the start(), skipping the init ().
• Paint()– The applet begins the execution of the program by calling the paint() method. The paint() has a parameter known as Graphics, and Graphics g helps in the execution of the program in painting different parameters.
• Stop()– The Stop() is called when the user leaves the HTML document and moves to the applet. Start() restarts them whenever Stop() terminates the program and then applies the changes.
• Destroy()– The applet invokes the Destroy() function when it needs to be completely removed from memory.

Examples of Applets in Java

Below, we provide several examples of Applets in Java:

Example #1

In the coding example, we will see a basic version of the Hello World applet. The figure below illustrates the representation of an essential Applet, Hello World, in the BlueJ Java programming platform.

Whenever we try to run the applet, the applet provides the screen below, which shows us many options to select from within a range of options. In the screen below, we can generate a web page, run an applet in the Applet Viewer or run the applet in a Web browser. We have provided several options for running an applet in the BlueJ Programming platform. The applet’s height and width can also be provided in the box, and depending on the height and width provided, the applet runs, making a distinct applet serving solutions for various problems.

Now we see the example of the sample coding and import packages to present the Hello World Sample Code. In this program, we implement packages such as Applet and Graphics. Developers use the Graphics g object to paint and render output in a web browser or any desired medium.

Code:

import java.applet.Applet;
import java.awt.Graphics;
public class HelloWorld extends Applet
{
// Overriding paint() method
@Override
public void paint(Graphics g)
{
g.drawString("Hello World@ Great to be here!!!", 50, 50);
}
}

Output:

The example also provides a sample output. Developers can include additional comments in a Java applet to generate various other outputs.

Output:

Now, we can do many functions on the applet, such as Restart, Reload, Stop, Save, Start, and Clone. These are functionalities that the applet provides with various stages.

Example #2

In the next coding example, we will see more aspects of Java applets in which we see the basic functionality of Java applets. In the next Java applet, we change the height and width of the Java applet, and we make some fundamental changes in the functionality. The writing comes more in the middle. Below is an example of a coding sample that executes to print the “Hello World” statement:

Code:

import java.applet.Applet;
import java.awt.Graphics;
public class HelloWorld extends Applet
{
// Overriding paint() method
@Override
public void paint(Graphics g)
{
g.drawString("Hello World!!! Great to be here!!!", 150,150);
}
}

Output:

Advantages and Disadvantages of Applets in Java

There are several advantages and disadvantages of running a Java applet.

Advantages

Some of the advantages listed down are as follows:

• The applet works on the client side; hence there is a meager response time.
• The applet is very secure and robust.
• It can execute under various operating systems, including Unix, Linux, and macOS operating systems.
• Combining the applet with HTML, CSS, and Javascript enhances the web page’s functionality.
• The applet is very easy to build and contains very little redundancy.

Disadvantages

The document can illustrate the non-use support and highlight some of the disadvantages of Applets. The disadvantages are:

• The client side requires the presence of a plugin to execute the applet.
• Without the proper plugin, there is no execution of the applet on the client side.
• Making complex applets is quite complicated and hence is a disadvantage.

Conclusion

In this article, we see the basic functions of an applet, the lifecycle of an applet, as well as some basic programs as to how an applet runs in the Java programming language. Developers can create and implement highly complex applets using software like BlueJ and other tools for HTML and CSS. We stress the theory part of applets more than the programming concept for applets.

The above is the detailed content of Applets in Java. For more information, please follow other related articles on the PHP Chinese website!