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Java in a Nutshell

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Applets
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6.2 A First Applet

Figure 6.1 shows what is probably the simplest possible applet you can write in Java. Example 6.1 lists its code. This example introduces the paint() method, which is invoked by the applet viewer (or Web browser) when the applet needs to be drawn. This method should perform graphical output--such as drawing text or lines or displaying images--for your applet. The argument to paint() is a Graphics object that you use to do the drawing.

Figure 6.1: A simple applet

[Graphic: Figure 6-1]

Example 6.1: The Simplest Applet

import java.applet.*;   // Don't forget this import statement!
import java.awt.*;          // Or this one for the graphics!
public class FirstApplet extends Applet {
  // This method displays the applet.
  // The Graphics class is how you do all drawing in Java.
  public void paint(Graphics g) {
    g.drawString("Hello World", 25, 50);
  }
}

To display an applet, you need an HTML file that references it. Here is an HTML fragment that can be used with our first applet:

<APPLET code="FirstApplet.class" width=150 height=100>
</APPLET>

With an HTML file that references the applet, you can now view the applet with an applet viewer or Web browser. Note that the width and height attributes of this HTML tag are required. See Chapter 15, Java-Related HTML Tags for more details on the HTML <APPLET> tag. For most applet examples in this book, we show only the Java code and not the corresponding HTML file that goes with it. Typically, that HTML file contains a tag as simple as the one shown here.


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