WinForms TreeView Развернуть / Свернуть случайно не работает

Нижеприведенный код должен работать

    int[] mynumbers = {3,4};
    BitSet compressedNumbers = new BitSet(mynumbers.length*3);
    // let's say you encoded 3 as 101 and 4 as 010
    String myNumbersAsBinaryString = "101010"; 
    for (int i = 0; i < myNumbersAsBinaryString.length(); i++) {
        if(myNumbersAsBinaryString.charAt(i) == '1')
            compressedNumbers.set(i);
    }
    String path = Resources.getResource("myfile.out").getPath();
    ObjectOutputStream outputStream = null;
    try {
        outputStream = new ObjectOutputStream(new FileOutputStream(path));
        outputStream.writeObject(compressedNumbers);
    } catch (IOException e) {
        e.printStackTrace();
    }