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Detailed introduction to what is Java applet

Y2JOriginal: 2017-05-18 10:10:212964browse

Details

Applets can be translated as small applications. Java Applets are small applications written in Java language. They can be directly embedded into web pages and can produce special effects. Web pages that contain Applets are called Java-powered pages and can be called Java-supported web pages.

When a user accesses such a webpage, the Applet is downloaded to the user's computer for execution, but only if the user is using a Java-enabled web browser. Since the Applet is executed on the user's computer, its execution speed is not limited by network bandwidth or Modem access speed. Users can better appreciate the multimedia effects produced by Applets on web pages.

In Java Applet, you can realize graphics drawing, font and color control, animation and sound insertion, human-computer interaction and network communication and other functions. Applet also provides a window environment development tool called Abstract Window Toolkit (AWT). AWT uses the GUI elements of the user's computer to create standard graphical user interfaces, such as windows, buttons, scroll bars, etc. Currently, there are many Applet examples on the Internet to vividly demonstrate these functions. Readers can visit the corresponding web pages to view their effects.

The working principle of Applet.

The HTML file code of the web page containing Applet contains a pair of tags such as 082dedeb30a00d0e6e2cdb74a392fac3 When this pair of tags is encountered, the corresponding applet code is downloaded and executed on the local computer.

Example

Homepage with an Applet

<html>
<title> An Example Homepage </title>
<h1> Welcome to my homepage! </h1>
This is an example homepage， you can see an applet in it。
<p> <br>
<applet code=“Example.class” width = 300 height=300>
<param name = img value="example.gif">
</applet>
</html>

The above example is the HTML file code of a simple homepage. The e388a4556c0f65e1904146cc1a846bee in the fifth line of code is to ensure that the Applet appears on a new line. Without it, the Applet will appear immediately after the last word of the previous line. The sixth and seventh lines of the code are about some parameters of the Applet. The sixth line is the required Applet parameter, which defines the compiled file name containing the Applet bytecode, with the suffix usually ".class"; and the initial width and height of the Applet in pixels. The seventh line is the additional Applet parameter, which is specified by a separate tag to specify the subsequent name and value. Here, the value of img is "example.gif', which represents a graphics file name.

Applet's download is the same as the graphic file, and it can be displayed on the screen after several seconds. The program on the computer runs at the same speed.

When the Applet is executed on the user's computer, it can also download other resources, such as sound files, image files or more Java Code, some Applets also allow users to perform interactive operations. But this requires repeated links and downloads, so the speed is very slow. This is an urgent problem to be solved. A good way to think of is to use something like high-speed caching's technology temporarily saves each downloaded file on the user's hard drive. Although it takes more time when using it for the first time, when it is used again, it only needs to read the file directly from the hard drive ##Without connecting to the Internet, the performance can be greatly improved

import java.awt.*;
import java.applet.*;
public class HelloApplet extends Applet{
public void paint(Graphics g){
g.drawString("Helloworld!",50,25);
}
}

8c59f7d462183052d3f1f9c0dc7e13e9

<HTML>
<HEAD>
<TITLE>　HTML Test Page
</TITLE>
</HEAD>
<BODY>
HelloApplet will appear below in a Java enbaled broswer.<BR>
<APPLET
CODEBASE="."
CODE = "HelloApplet.class"
NAME = "TestApplet"
WIDTH = 400
HEIGHT = 300
HSPACE = 0
VSPACE = 0
ALIGN = middle
>
</APPLET>
</BODY>
</HTML>

(Java Applet program. It cannot be run alone and must be embedded into a Web page written in HTML language, and the execution is controlled through a Java-compatible browser)

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