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My File Clears Everytime I Run My Code - Java

I have Server-Client messenger - not important - and I have a settings file to store the settings, but for some reason when I run the code, the settings file clears.
Here is the code that makes the settings file and directory:
boolean exists = new File(System.getProperty("user.home")+"\\Documents\\Messenger Server").mkdir();
File directory = new File(System.getProperty("user.home")+"\\Documents\\Messenger Server");
File settingsFile = new File(System.getProperty("user.home")+"\\Documents\\Messenger Server\\settings.txt");
if(exists){
try {
directory.createNewFile();
System.out.println("Created");
} catch (IOException e) {
e.printStackTrace();
}
}
if(!settingsFile.exists()){
try {
settingsFile.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("Created Settings.txt");
System.out.println(settingsFile.getAbsolutePath());
}
And this is the code that reads and writes to the file:
try {
FileReader fileReader = new FileReader(settingsFile);
FileWriter fileWriter = new FileWriter(settingsFile);
BufferedReader bf = new BufferedReader(fileReader);
BufferedWriter bw = new BufferedWriter(fileWriter);
}catch(IOException b){
b.printStackTrace();
}
ArrayList<String> settingList = new ArrayList<String>();
for (int i = 0; i < 6; i++) {
try {
settingList.add(bf.readLine());
} catch (IOException ex) {
ex.printStackTrace();
}
}
if(!settingList.get(0).equals("alwaysOnTop=true")&&!settingList.get(0).equals("alwaysOnTop=false")){
try {
bw.write("alwaysOnTop=false");
} catch (IOException ex) {
ex.printStackTrace();
}
}

The FileWriter constructor can take a boolean argument ( FileWriter(File file, boolean append) ), which if true makes the FileWriter append to the file instead of overwriting it every time. Like this:
FileWriter fileWriter = new FileWriter(settingsFile, true);

The answer from #JustusG is correct.
Still, I would not recommend using .txt files to keep the settings of your app.
Since they are hard to maintain, you may have duplicate settings (because of appending...) and so on.
I would recommend using .properties files. At the end of the day they do the same thing, it's just that .properties files have classes to read and to write your settings/properties.
Here is an example:
Properties prop = new Properties();
File propFile = new File("path/to/app.properties");
InputStream in = new FileInputStream(propFile); // Open the prop file
prop.load(in); // Load it in the Properties object
prop.setProperty("setting1", "value1"); // Setting a new setting to what you need OR setting an old setting to a new value.
String value2 = prop.getProperty("setting2"); // Reading a property
//And at the end, writing the properties that you changed (without duplicates)
prop.store(new FileOutputStream("xyz.properties"), null);

Java write to the file nonreadable sumbols

This is my method, he create new object "predmet". class "AddNewObject" return me predmet type (name, description).
AddNewPredmet addnewpredmet = new AddNewPredmet();
listPredmet.add(AddNewPredmet.AddPredmet());
StorageInFile.savePredmet(listPredmet);
All working. But I have a problem with the result written in the file. The output file has symbols that are not readable as shown -
¬н sr java.util.ArrayListxЃТ™Зaќ I sizexp w sr entity.PredmetїБц)Зя| L Descriptiont Ljava/lang/String;L PNameq ~ xpt testt testx
The following is the function that writes to the file
public class StorageInFile {
static void savePredmet(List<Predmet> listPredmet) {
FileOutputStream fos = null;
ObjectOutputStream oos = null;
try {
fos = new FileOutputStream("Predmet.txt");
oos = new ObjectOutputStream(fos);
oos.writeObject(listPredmet);
oos.flush();
oos.close();
} catch (FileNotFoundException ex) {
Logger.getLogger(StorageInFile.class.getName())
.log(Level.SEVERE, "Нет такого файла", ex);
} catch (IOException ex) {
Logger.getLogger(StorageInFile.class.getName())
.log(Level.SEVERE, "Не могу записать", ex);
}
}}
How i can fix this? I think about method toString(), but i cant add this method to this code.

Try using a buffered writer and use UTF-8 capable viewer to see the file. You are trying to using a tool that assumes a one-byte encoding, such as the Windows-125x encodings. Notepad is an example of such a tool. So using the capable viewer you can look at it.
Also it would help to show what’s in your file

If you expected to print the contents of every instance of Predmet in the List<> then you could try the following.
Implement to the toString() method in Class Predmet
Try the following snippet to write to file.
FileWriter writer = new FileWriter("sample.txt");
try {
int size = listPredMet.size();
for (int index =0; index < size; index++){
writer.write(listPredMet.get(index).toString());
writer.flush();
}
}catch(Exception e){
e.printStackTrace();
}finally{
writer.close()
}

Can not read any text file

First of all, I would like you to say that I am quite new here and I'm also a beginner in Android Studio and Java.
My problem/question is:
I have an App in Android Studio which should write a string to a text file at a specific point and also should read the same file on App startup.
Writing to the file is working but not reading. When I create a text file manually, and insert it manually to the folder it reads the string.
I already added permissions and try to find my error with LogCat but I have no clue at the moment what could be wrong.
Variables:
File root = android.os.Environment.getExternalStorageDirectory();
File dir = new File(root.getAbsolutePath() + "/myApp");
My reading function:
String myData = "";
try {
FileReader fileIn = new FileReader(dir + "/data.txt");
Scanner input = new Scanner(fileIn);
while (input.hasNextLine()) {
String line = input.nextLine();
myData = myData + line;
}
input.close();
} catch (Exception ex) {
ex.printStackTrace();
}
My writing function:
try {
File file = new File(dir, "data.txt");
FileOutputStream f = new FileOutputStream(file);
PrintWriter pw = new PrintWriter(f);
pw.println("answer42");
pw.flush();
pw.close();
f.close();
} catch (Exception ex) {
ex.printStackTrace();
}

Saving String Input on Android

Right, I've been trying to find a solution to this for a good while, but it's just not working for some reason.
In short, what I want to do is save every input String the user inputs into a file. Every time the activity is created again, I want to re-input these strings into a new instance of an object.
This code is what I use to create the file and read info from it, used in the onCreate() method of activity
try {
String brain = "brain";
File file = new File(this.getFilesDir(), brain);
if (!file.exists()) {
file.createNewFile();
}
BufferedReader in = new BufferedReader(new FileReader(file));
String s; // This feeds the object MegaAndroid with the strings, sequentially
while ((s = in.readLine()) != null) {
MegaAndroid.add(s);
}
in.close();
} catch (IOException e) {
e.printStackTrace();
}
After that, every time the user inputs some text, the strings are saved onto the file:
try {
String brain = "brain";
File file = new File(this.getFilesDir(), brain);
if (!file.exists()) {
file.createNewFile();
}
BufferedWriter out = new BufferedWriter(new FileWriter(file));
out.write(message); // message is a string that holds the user input
out.close();
} catch (IOException e) {
e.printStackTrace();
}
For some reason, however, every time the application is killed, the data is lost.
What am I doing wrong?
EDIT: Also, if I were to access this file from another class, how can I?

As we discussed in the commend section the chief problem with the code is that your execution of FileWriter occurred prior to your FileReader operation while truncating the file. For you to maintain the file contents you want to set the write operation to an append:
BufferedWriter out = new BufferedWriter(new FileWriter(file,true));
out.write(message);
out.newLine();
out.close();
However, if every entry on the EditText is received then shipped into the file you'll just be writing data byte after byte beside it. It is easy to get contents similar to
This is line #1This is line #2
Instead of the desired
This is line #1
This is line #2
which would be corrected by having the BufferedWriter pass a newline after each write to the file.

This is what I do for file reading.
try{
File sdCard = Environment.getExternalStorageDirectory();
File dir = new File (sdCard.getAbsolutePath() + "/whereyouwantfile");
dir.mkdirs();
Log.d(TAG,"path: "+dir.getAbsolutePath());
File file = new File(dir, "VERSION_FILENAME");
FileInputStream f = new FileInputStream(file);
//FileInputStream fis = context.openFileInput(VERSION_FILENAME);
BufferedReader reader = new BufferedReader(new InputStreamReader(f));
String line = reader.readLine();
Log.d(TAG,"first line versions: "+line);
while(line != null){
Log.d(TAG,"line: "+line);
//Process line how you need
line = reader.readLine();
}
reader.close();
f.close();
}
catch(Exception e){
Log.e(TAG,"Error retrieving cached data.");
}
And the following for writing
try{
File sdCard = Environment.getExternalStorageDirectory();
File dir = new File (sdCard.getAbsolutePath() + "/whereyouwantfile");
dir.mkdirs();
File file = new File(dir, "CONTENT_FILENAME");
FileOutputStream f = new FileOutputStream(file);
//FileOutputStream fos = context.openFileOutput(CONTENT_FILENAME, Context.MODE_PRIVATE);
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(f));
Set<String> keys = Content.keySet();
for(String key : keys){
String data = Content.get(key);
Log.d(TAG,"Writing: "+key+","+data);
writer.write(data);
writer.newLine();
}
writer.close();
f.close();
}
catch(Exception e){
e.printStackTrace();
Log.e(TAG,"Error writing cached data.");
}
You can use the private mode if you don't want the rest of the world to be able to see your files, but it is often useful to see them when debugging.

Test if file exists

I'm trying to open a file in android like this :
try
{
FileInputStream fIn = context.openFileInput(FILE);
DataInputStream in = new DataInputStream(fIn);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
if(in!=null)
in.close();
}
catch(Exception e)
{ }
, but in case the file does not exists a file not found exception is thrown . I'd like to know how could I test if the file exists before attempting to open it.

I think the best way to know if a file exists, without actually trying to open it, is as follows:
File file = getContext().getFileStreamPath(FILE_NAME);
if(file.exists()) ...

The documentation says Context.openFileInput either returns an inputStream (file found) or throws a FileNotFoundException (not found)
http://developer.android.com/reference/android/content/Context.html#openFileInput(java.lang.String)
So it looks like the exception is your "test".
You could also try using standard
java.io.File file = new java.io.File(PATHTOYOURCONTEXT , FILE);
if (file.exists()) {
FileInputStream fIn = new FileInputStream(file);
}
But that is not recommended. Context.openFileInput() and Context.openFileOutput() make sure you stay in your applications storage context on the device, and that all of your files get
deleted when your app gets uninstalled.

With the standard java.io.File this is the function I have created, and works correctly:
private static final String APP_SD_PATH = "/Android/data/com.pkg.myPackage";
...
public boolean fileExistsInSD(String sFileName){
String sFolder = Environment.getExternalStorageDirectory().toString() +
APP_SD_PATH + "/Myfolder";
String sFile=sFolder+"/"+sFileName;
java.io.File file = new java.io.File(sFile);
return file.exists();
}

why dont you just catch the FileNotFound exception and take that as the file not being present.

If you want to ensure a file exists (i.e. if it doesn't exist create a new one, if it does then don't erase it) then use File.createNewFile:
https://docs.oracle.com/javase/7/docs/api/java/io/File.html#createNewFile()
e.g.
{
String pathName = <file path name>
File file = new File (pathName);
Uri pathURI = Uri.fromFile (file);
boolean created;
String mIOException = "";
String mSecException = "";
try
{
created = file.createNewFile();
if (created)
{
ctxt.sendBroadcast (new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, pathURI));
}
}
catch (IOException ioex)
{
mIOException = ioex.getMessage();
}
catch (SecurityException sex)
{
mSecException = sex.getMessage();
}
}

If you want to open a file in any case (i.e. if it doesn't exist create a new one, if it does append to the old one) you can use this, no testing necessary:
public static void write_custom_log(String message){
File root = Environment.getExternalStorageDirectory();
try{
BufferedWriter fw = new BufferedWriter(new FileWriter(new File("/mnt/sdcard/tjb_tests/tjb_log_file.txt"),true));
if (root.canWrite()){
fw.write(message);
fw.close();
}
} catch (IOException e) {
Log.e("One", "Could not write file " + e.getMessage());
}
}

My suggestion is to check length of the file. if file.length() returns 0 that means file doesn't exist.