Question

I have a problem with java applet and graphics. I’m trying to run it in Eclipse and it fails.
Im new in java and i hope you can help me.
I have two files: Say.java and SayWhat.java.
Say.java:

public class Say {
    SayWhat word = new SayWhat("Hello World");

}

SayWhat.java:

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

@SuppressWarnings("serial")
public class SayWhat extends Applet {
     Graphics g;
     String what;
    public SayWhat(String what) {
        this.what=what;
    }
    public void paint(Graphics g){
        g.drawString(what, 20, 20);
    }
}

Error that appears is:

load: SayWhat.class can't be instantiated.
java.lang.InstantiationException: SayWhat
    at java.lang.Class.newInstance0(Unknown Source)
    at java.lang.Class.newInstance(Unknown Source)
    at sun.applet.AppletPanel.createApplet(Unknown Source)
    at sun.applet.AppletPanel.runLoader(Unknown Source)
    at sun.applet.AppletPanel.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

Can you please tell me what am i doing wrong?

Answer 1

An applet needs to have a public no-arg constructor (either by having an explicit public no-arg constructor, or by having no explicit constructors at all; in the latter case, the compiler will supply a public no-arg constructor as a default). Your class’s sole constructor takes an argument:

public SayWhat(String what) {

so the class can’t be instantiated without that argument, so it can’t be used as an applet.