Solution

HTML Interface to Applet

<APPLET CODEBASE="/applets/magelang/AWT-Training/classes/" CODE="EMailTextFieldTest.class" WIDTH=300 HEIGHT=20 ALIGN=CENTER></APPLET>

Java Code

import java.awt.*;

public class EMailTextFieldTest extends java.applet.Applet {

    public void init() {
        setLayout(new GridLayout(1,1));
        EMailTextField test = new EMailTextField();
        add(test);
    }
}

/**
 * Component containing both a Label and a TextField.
 * Used for entering and validating an e-mail address.
 */
class EMailTextField extends LabeledTextField {

    public EMailTextField() {
        super("E-Mail Address");
    }

    public void verify() {
        String address = text.getText().toUpperCase();
        if (!address.endsWith(".COM") &&
            !address.endsWith(".EDU") &&
            !address.endsWith(".GOV") &&
            !address.endsWith(".MIL") &&
            !address.endsWith(".ORG") &&
            !address.endsWith(".NET") ) {
            System.err.println("Invalid internet domain:  " +
                               "Please enter again.");
            text.setText("");
        }

        if (address.indexOf("@") <= 0) {
            System.err.println("Invalid user name:  " +
                               "Please enter again.");
            text.setText("");
        }
    }
}