Related NetBeans bug:
https://netbeans.org/bugzilla/show_bug.cgi?id=239364

Prior JDK8 the document listeners were fired INSIDE of the document lock upon insert while in JDK8 they are fired OUTSIDE of the lock. That means that the DocumentListener implementations can no longer rely that the offset and length contained in the document events correspond to the actual document state.

The regression was introduced with a fix of issue JDK-7146146.

The following test demonstrates that a document listener can no longer rely on the document's content on JDK8 (the test passes fine on JDK7):

    public void testInsertedTextIsPresent() throws Exception {
        final PlainDocument doc = new PlainDocument();
        final CountDownLatch insertDone = new CountDownLatch(1);
        final CountDownLatch removeDone = new CountDownLatch(1);

        doc.addDocumentListener(new DocumentListener() {
            public void insertUpdate(DocumentEvent evt) {
                insertDone.countDown();
                try {
                    removeDone.await(1, TimeUnit.SECONDS);
                } catch (InterruptedException ex) {
                    throw new IllegalStateException(ex);
                }

                try {
                    String insertedText = evt.getDocument().getText(evt.getOffset(), evt.getLength());
                } catch (BadLocationException ex) {
                    throw new IllegalStateException(
                            "Inserted text not present in document !!! docLen=" + doc.getLength(), ex);
                }
            }
            public void removeUpdate(DocumentEvent evt) {
            }
            public void changedUpdate(DocumentEvent evt) {
            }
        });
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    insertDone.await();
                    doc.remove(0, doc.getLength());
                    removeDone.countDown();
                } catch (Exception ex) {
                    throw new IllegalStateException(ex);
                }
            }
        }).start();

        doc.insertString(0, "Hello", null);
        
    }