Serialization issue (probably?)

Question

Greetings fellow Java devs.
I am fairly new to the subject of serialization. I am developing production code for a company and I need another pair of eyes to look at what I'm doing and help me figure it out. I have spent days debugging this god forsaken problem and it's just becoming a huge hindrance.
I am trying to manage a LinkedList data structure with methods for "adding (inserting)" "removing" "setting" etc. There are two lists, a "LinkedList<WI_Item> watchList" and "LinkedList<WI_Item> ignoreList" of custom-Objects ("WI_Item" just a DS to hold info needed).
The problem: The "System.outs" in the "remove" and "insert" methods work fine, as expected. The "watchList" and "ignoreList" LinkedLists update as expected. However, it seems that every other time a reference is made to those objects, they have "reset" to what they were when the file was originally read in by the constructor. In other words, the Objects appear to change for a short while, and then they go back to their original state.
What am I doing wrong? Thanks for your help. I haven't got any energy to debug this anymore. :(
    public void removeFromWatch(WI_Item item){
        System.out.println("Old WatchList: " + watchList);
        watchList.remove(item);
        System.out.println("New WatchList: " + watchList);
        setWatchList(watchList);
        System.out.println("Same WatchList: " + watchList);
    public void removeFromIgnore(WI_Item item){
        System.out.println("Old IgnoreList: " + ignoreList);
        ignoreList.remove(item);
        System.out.println("New IgnoreList: " + ignoreList);
        setIgnoreList(ignoreList);
        System.out.println("Same IgnoreList: " + ignoreList);
    public void insertIntoWatch(WI_Item item){
        System.out.println("Old WatchList: " + watchList);
        watchList.add(item);
        System.out.println("New WatchList: " + watchList);
        setWatchList(watchList);
        System.out.println("Same WatchList: " + watchList);
    public void insertIntoIgnore(WI_Item item){
        System.out.println("Old ignoreList: " + ignoreList);
        ignoreList.add(item);
        System.out.println("New ignoreList: " + ignoreList);
        setIgnoreList(ignoreList);
        System.out.println("Same IgnoreList: " + ignoreList);I overrode the toString method for the "WI_Item" object so this displays as if it was printing a LinkedList of Strings (" [Item 1, Item 2, Item 3] ")
And here are the two methods you will notice in that code (setWatchList, setIgnoreList) which handle the writing of the object.
    public void setWatchList(LinkedList<WI_Item> watchList){
        FileOutputStream fos = null;
        ObjectOutputStream watchOOS = null;
        try{
            fos = new FileOutputStream(watchListFile);
            watchOOS = new ObjectOutputStream(fos);
            watchOOS.writeObject(watchList);
            fos.close();
            watchOOS.close();
        } catch(Exception e){
            JOptionPane.showMessageDialog(new JFrame(),
                "Error writing watch list " + e.getMessage(),
                "Error writing watch list " + e.getMessage(),
                JOptionPane.INFORMATION_MESSAGE);
    public void setIgnoreList(LinkedList<WI_Item> ignoreList){
        FileOutputStream fos = null;
        ObjectOutputStream ignoreOOS = null;
        try{
            fos = new FileOutputStream(ignoreListFile);
            ignoreOOS = new ObjectOutputStream(fos);
            ignoreOOS.writeObject(ignoreList);
            fos.close();
            ignoreOOS.close();
        } catch(Exception e){
            JOptionPane.showMessageDialog(new JFrame(),
                "Error writing ignore list " + e.getMessage(),
                "Error writing ignore list " + e.getMessage(),
                JOptionPane.INFORMATION_MESSAGE);
    }The reading of the object (from the file) is done in the constructor, and only there. Whenever I need to "read" the list, I just return the LinkedLists.
    public LinkedList<WI_Item> getIgnoreList(){
        return ignoreList;
    public LinkedList<WI_Item> getWatchList(){
        return watchList;
    }Here is the constructor (which reads in the Objects once and only once):
    LinkedList<WI_Item> watchList;
    LinkedList<WI_Item> ignoreList;
    String watchListPath = "watchlist";
    String ignoreListPath = "ignorelist";
    InputStream ignoreListStream;
    InputStream watchListStream;
    File ignoreListFile;
    File watchListFile;
    URI ignoreListUri;
    URI watchListUri;
    ObjectInputStream ignoreOIS;
    ObjectInputStream watchOIS;
    public WatchIgnoreManager(){
        try{
            ignoreListStream = Main.class.getResourceAsStream(ignoreListPath);
            watchListStream = Main.class.getResourceAsStream(watchListPath);
            ignoreListUri = Main.class.getResource(ignoreListPath).toURI();
            watchListUri = Main.class.getResource(watchListPath).toURI();
            ignoreListFile = new File(ignoreListUri);
            watchListFile = new File(watchListUri);
            ignoreOIS = new ObjectInputStream(ignoreListStream);
            watchOIS = new ObjectInputStream(watchListStream);
            watchList = (LinkedList<WI_Item>)watchOIS.readObject();
            ignoreList = (LinkedList<WI_Item>)ignoreOIS.readObject();
        } catch(Exception e){
            e.printStackTrace();
            JOptionPane.showMessageDialog(new JFrame(),
                "DataWriter Error " + e.getMessage(),
                "DataWriter Error " + e.getMessage(),
                JOptionPane.INFORMATION_MESSAGE);
        } finally {
            try{
                ignoreListStream.close();
                watchListStream.close();
                ignoreOIS.close();
                watchOIS.close();
            } catch(Exception e){
                e.printStackTrace();
...

Answer 1

Here is the full code for this class, if it helps.
package firebirdprogram;
/* imports edited out for space */
public class WatchIgnoreManager {
    LinkedList<WI_Item> watchList;
    LinkedList<WI_Item> ignoreList;
    String watchListPath = "watchlist";
    String ignoreListPath = "ignorelist";
    InputStream ignoreListStream;
    InputStream watchListStream;
    File ignoreListFile;
    File watchListFile;
    URI ignoreListUri;
    URI watchListUri;
    ObjectInputStream ignoreOIS;
    ObjectInputStream watchOIS;
    public WatchIgnoreManager(){
        try{
            ignoreListStream = Main.class.getResourceAsStream(ignoreListPath);
            watchListStream = Main.class.getResourceAsStream(watchListPath);
            ignoreListUri = Main.class.getResource(ignoreListPath).toURI();
            watchListUri = Main.class.getResource(watchListPath).toURI();
            ignoreListFile = new File(ignoreListUri);
            watchListFile = new File(watchListUri);
            ignoreOIS = new ObjectInputStream(ignoreListStream);
            watchOIS = new ObjectInputStream(watchListStream);
            watchList = (LinkedList<WI_Item>)watchOIS.readObject();
            ignoreList = (LinkedList<WI_Item>)ignoreOIS.readObject();
            ignoreOIS.close();
            watchOIS.close();
            ignoreListStream.close();
            watchListStream.close();
        } catch(Exception e){
            e.printStackTrace();
            JOptionPane.showMessageDialog(new JFrame(),
                "DataWriter Error " + e.getMessage(),
                "DataWriter Error " + e.getMessage(),
                JOptionPane.INFORMATION_MESSAGE);
    public void insertIntoWatch(String part_no, String description){
        insertIntoWatch(new WI_Item(part_no, description));
    public void insertIntoIgnore(String part_no, String description){
        insertIntoIgnore(new WI_Item(part_no, description));
    public void insertIntoWatch(WI_Item item){
        System.out.println("Old WatchList: " + watchList);
        watchList.add(item);
        System.out.println("New WatchList: " + watchList);
        setWatchList(watchList);
        System.out.println("Same WatchList: " + watchList);
    public void insertIntoIgnore(WI_Item item){
        System.out.println("Old ignoreList: " + ignoreList);
        ignoreList.add(item);
        System.out.println("New ignoreList: " + ignoreList);
        setIgnoreList(ignoreList);
        System.out.println("Same IgnoreList: " + ignoreList);
    public void removeFromWatch(String part_no){
        WI_Item itemToDelete = null;
        for(WI_Item item : getWatchList()){
            if(item.getPart_no().equals(part_no)){
                itemToDelete = item;
        removeFromWatch(itemToDelete);
    public void removeFromIgnore(String part_no){
        WI_Item itemToDelete = null;
        for(WI_Item item : getIgnoreList()){
            if(item.getPart_no().equals(part_no)){
                itemToDelete = item;
        removeFromIgnore(itemToDelete);
    public void removeFromWatch(WI_Item item){
        System.out.println("Old WatchList: " + getWatchPartNos());
        watchList.remove(item);
        System.out.println("New WatchList: " + getWatchPartNos());
        setWatchList(watchList);
        System.out.println("Same WatchList: " + getWatchPartNos());
    public void removeFromIgnore(WI_Item item){
        System.out.println("Old IgnoreList: " + getIgnorePartNos());
        ignoreList.remove(item);
        System.out.println("New IgnoreList: " + getIgnorePartNos());
        setIgnoreList(ignoreList);
        System.out.println("Same IgnoreList: " + getIgnorePartNos());
    public LinkedList<String> getWatchPartNos(){
        System.out.println("Get Watch Part Nos " + getWatchList());
        LinkedList<String> results = new LinkedList<String>();
        for(WI_Item item : getWatchList()){
            results.add(item.getPart_no());
        return results;
    public LinkedList<String> getIgnorePartNos(){
        System.out.println("Get Ignore Part Nos " + getIgnoreList());
        LinkedList<String> results = new LinkedList<String>();
        for(WI_Item item : getIgnoreList()){
            results.add(item.getPart_no());
        return results;
    public LinkedList<String> getBothPartNos(){
        LinkedList<String> results = new LinkedList<String>();
        for(String s : getWatchPartNos()){
            results.add(s);
        for(String s : getIgnorePartNos()){
            results.add(s);
        System.out.println("Returning " + results);
        return results;
    public LinkedList<WI_Item> getIgnoreList(){
        return ignoreList;
    public LinkedList<WI_Item> getWatchList(){
        return watchList;
    public LinkedList<WI_Item> getBoth(){
        LinkedList<WI_Item> both = new LinkedList<WI_Item>();
        for(WI_Item item : getWatchList()){
            both.add(item);
        for(WI_Item item : getIgnoreList()){
            both.add(item);
        return both;
    public void setWatchList(LinkedList<WI_Item> watchList){
        FileOutputStream fos = null;
        ObjectOutputStream watchOOS = null;
        try{
            fos = new FileOutputStream(watchListFile);
            watchOOS = new ObjectOutputStream(fos);
            watchOOS.writeObject(watchList);
            watchOOS.close();
            fos.close();
        } catch(Exception e){
            JOptionPane.showMessageDialog(new JFrame(),
                "Error writing watch list " + e.getMessage(),
                "Error writing watch list " + e.getMessage(),
                JOptionPane.INFORMATION_MESSAGE);
    public void setIgnoreList(LinkedList<WI_Item> ignoreList){
        FileOutputStream fos = null;
        ObjectOutputStream ignoreOOS = null;
        try{
            fos = new FileOutputStream(ignoreListFile);
            ignoreOOS = new ObjectOutputStream(fos);
            ignoreOOS.writeObject(ignoreList);
            ignoreOOS.close();
            fos.close();
        } catch(Exception e){
            JOptionPane.showMessageDialog(new JFrame(),
                "Error writing ignore list " + e.getMessage(),
                "Error writing ignore list " + e.getMessage(),
                JOptionPane.INFORMATION_MESSAGE);
}