The public class windchill implements ActionListener

W in windchill is lowercase,

In the 40-line constructor you wrote, the w of windchill is capitalized, so it is not regarded as a constructor.

Just change the case of two words.

It was careless to make this mistake.

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Here:

//Display a graphical user interface

window.show()。

}

If the JRE you use is above 1.4, then the show method is out of date, and you should use window.setvisible (true);