Applet

Main article: Java applet

Java applets are programs that are embedded in other applications, typically in a Web page displayed in a Web browser.

// Hello.java
import java.applet.Applet;
import java.awt.Graphics;

public class Hello extends Applet {
public void paint(Graphics gc) {
gc.drawString("Hello, world!", 65, 95);
}
}

The import statements direct the Java compiler to include the java.applet.Applet and java.awt.Graphics classes in the compilation. The import statement allows these classes to be referenced in the source code using the simple class name (i.e. Applet) instead of the fully qualified class name (i.e. java.applet.Applet).

The Hello class extends (subclasses) the Applet class; the Applet class provides the framework for the host application to display and control the lifecycle of the applet. The Applet class is an Abstract Windowing Toolkit (AWT) Component, which provides the applet with the capability to display a graphical user interface (GUI) and respond to user events.

The Hello class overrides the paint(Graphics) method inherited from the Container superclass to provide the code to display the applet. The paint() method is passed a Graphics object that contains the graphic context used to display the applet. The paint() method calls the graphic context drawString(String, int, int) method to display the "Hello, world!" string at a pixel offset of (65, 95) from the upper-left corner in the applet's display.












An applet is placed in an HTML document using the HTML element. The applet tag has three attributes set: code="Hello" specifies the name of the Applet class and width="200" height="200" sets the pixel width and height of the applet. Applets may also be embedded in HTML using either the object or embed element[16], although support for these elements by Web browsers is inconsistent.[17] However, the applet tag is deprecated, so the object tag is preferred where supported.

The host application, typically a Web browser, instantiates the Hello applet and creates an AppletContext for the applet. Once the applet has initialized itself, it is added to the AWT display hierarchy. The paint method is called by the AWT event dispatching thread whenever the display needs the applet to draw itself.

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