###@###.### (Ken Arnold - Sun Labs)
RunApplet.java:8: Invalid method declaration, return type required.
    public StopButton(Thread t, Window parent)
           ^
java.lang.NullPointerException
        at java.tools.tree.NewInstanceExpression.codeValue(NewInstanceExpression.java)
        at java.tools.javac.SourceField.codeInit(SourceField.java)
        at java.tools.javac.SourceField.codeInit(SourceField.java)
        at java.tools.javac.SourceClass.compileClass(SourceClass.java)
        at java.tools.javac.SourceClass.compile(SourceClass.java)
        at java.tools.javac.Main.compile(Main.java)
        at java.tools.javac.Main.main(Main.java)
javac: An exception has occurred in the compiler, please file a bug report.
/disk/pbil/RunApplet.java:5: Class StopButton already defined in RunApplet.java.
class StopButton extends Button {
      ^
/disk/pbil/RunApplet.java:8: Invalid method declaration, return type required.
    public StopButton(Thread t, Window parent)
           ^
/disk/pbil/RunApplet.java:21: Class RunApplet already defined in RunApplet.java.
class RunApplet extends Applet implements Runnable {
      ^
/disk/pbil/RunApplet.java:52: Class StopAction not found in type declaration.
protected static StopAction StopAction = new StopAction();
                                ^
/disk/pbil/RunApplet.java:52: Class StopAction not found in new.
protected static StopAction StopAction = new StopAction();
                                             ^

from the code below. I have just started adding the StopButton class.