ActionListener error

During java code on JFrame , using NetBeans 12 and JDK 15.0 , after creating a new ActionListener, a sudden exception occurring.
NetBeans just create a critical error and autocomplete ( at least) is not working, Neither code correction with red underline happens.
I needed to downgrade and remove JDK 15.0.1( from JDK.java.net) and go to 14 (openjdk-14+36_windows-x64_bin). Only then the error stop happening.

By adding the next code, on using ctrl+space on "new ActionL" the critical error (attached on log.txt) happened. When i was removing the ActionListener line, everything returned to normal.
Here is the part of the code that i was creating:

previousButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e)

{ previousButtonActionPerformed(e); }

});