Develop Reference

New line in reading file from user input

What I am trying to do is write a record to new line in my text file. Every time someone clicks sign up on my program, I want to call a method that opens a file and adds a record. This is what I have now:
To open the file:
try {
l = new Formatter("chineses.txt");
System.out.println("Did create");
} catch (Exception e){
System.out.println("Did not create");
}
To add the record:
public void addRecord(){
l.format("%s", nameField.getText());
}
Every time I put in a name in the name field and click sign up in my GUI, it always replaces whatever is on the first line in the text file.
How can I make it write to the second line while retaining what is on the first line?

Have you thought about using RandomAccessFile? You can seek to the end, then write.

According to the javadoc a formater created with a single String argument will first empty the file (truncate to zero length) before writing to it. This is why your file is not appended to. The program first removes whatever is in the file and then writes the new content to it when you call l.format().
What you probably want to do is format your data to a String using Formatter(). Open your record file for appending and then write that string to the file. This link should have plenty of details on how you might do this. (I googled "java open and write a file" to find that resource)

I can't understand why my application is not writing to a file

I am trying to add a way to save data to the android phone for my app. In the surfaceOnDestroyed I have added the following code.
try {
outputStream = getContext().openFileOutput("data.txt", Context.MODE_PRIVATE);
outputStream.write(current.getBytes());
outputStream.close();
System.out.println(current + " saved");
} catch(Exception e) {
e.printStackTrace();
}
Current is a string variable that I call earlier in my code that I print out here to show what it is when I am writing to the file. Each time I get that the variable is 2.
The data.txt file contains one line with a "0" initially placed in the file because the program reads from the file when the application is started.
When I check the data file after I destroy the object, the 0 is still in the file and has not changed to the 2.
I'm not sure what other information might be needed to solve this issue but I can not figure it out. Help much appreciated.

Clear contents of a file in Java using RandomAccessFile

I am trying to clear the contents of a file I made in java. The file is created by a PrintWriter call. I read here that one can use RandomAccessFile to do so, and read somewhere else that this is in fact better to use than calling a new PrintWriter and immediately closing it to overwrite the file with a blank one.
However, using the RandomAccessFile is not working, and I don't understand why. Here is the basic outline of my code.
PrintWriter writer = new PrintWriter("temp","UTF-8");
while (condition) {
writer.println("Example text");
if (clearCondition) {
new RandomAccessFile("temp","rw").setLength(0);
// Although the solution in the link above did not include ',"rw"'
// My compiler would not accept without a second parameter
writer.println("Text to be written onto the first line of temp file");
}
}
writer.close();
Running the equivalent of the above code is giving my temp file the contents:(Lets imagine that the program looped twice before clearCondition was met)
Example Text
Example Text
Text to be written onto the first line of temp file
NOTE: writer needs to be able to write "Example Text" to the file again after the file is cleared. The clearCondition does not mean that the while loop gets broken.

You want to either flush the PrintWriter to make sure the changes in its buffer are written out first, before you set the RandomAccessFile's length to 0, or close it and re-open a new PrintWriter to write the last line (Text to be written...). Preferably the former:
if (clearCondition) {
writer.flush();
new RandomAccessFile("temp","rw").setLength(0);

You'll be lucky if opening the file twice at the same time works. It isn't specified to work by Java.
What you should do is close the PrintWriter and open a new one without the 'append' parameter, or with 'append' set to 'false'.

How to clear text file in Android-java

I have text file in Android called "longlat.txt".
The text file contain latitude and longitude.
I save all the latitude and longitude to the text file using buffreader method.
After I finished using this app, I want to exit the app.
Means that I need to clear "longlat.txt" so that later on when I use the app, it will start the app without previous data that already being save to "longlat.txt".
So I provide a button called "Clear data" to clear the text file.
Now I need some ideas to clear "longlat.txt" file when user click "Clear data" button.
The only method that I'd used to clear the text file is I need to uninstall the app from my phone and reinstall it again .
I have tried :
public void Clear(View view){
PrintWriter writer;
try {
writer = new PrintWriter("longlat.txt");
writer.print("");
writer.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
After I clicked it, I want to check whether the text file already clear or not with click "Update" button, but when I click "Update" button, it still shows the old text file.

When you are closing the program (or any time you want to clear the file), you can simply just write empty data to the file, like so;
PrintWriter writer = new PrintWriter(file);
writer.print("");
writer.close();

How to save files in Java using variables in absolute path?

My problem is saving documents in Netbeans. I created a program using Java in Netbeans. At first you register (at the click on register button a new user Map is created with the name of the user), then you login with your user name and your password. When you are logged in, the program displays a new window where you can create documents. You can write text in TextArea. Then when you're finished with writing your text you click on Save button and the text you've written saves in a document named after the text you've given in a jTextField. So for every different login the absolute path changes.
This is my code in submit button:
//ccc is the name of user map
String ccc = LogIn.uporabnik1;
try{
FileWriter writer = new FileWriter("C:\\Users\\ALEKS\\Documents\\NetBeansProjects\\EasyEdit\\"+ccc+"\\"+FileName+".txt");
BufferedWriter bw = new BufferedWriter (writer);
jTextArea1.write(bw);
bw.close();
jTextArea1.setText("");
jTextArea1.requestFocus();
writer.close();
}
catch(Exception e){
JOptionPane.showMessageDialog(null, e);
}

It looks like there is a typo with an extra space in your path.
Note that as an alternative, if you use Java 7+, you can also use the Paths utility class to generate paths without having to deal with os specific separators (\\ or /):
Path path = Paths.get("C:/Users/ALEKS/Documents/NetBeansProjects/EasyEdit/"
+ ccc + "/" + FileName + ".txt");
And to write a string to a file:
String text = jTextArea1.getText();
Files.write(path, text.getBytes("UTF-8"));
That makes your code shorter and you don't have to manually create and close the streams.
Finally, for long-ish operations, you should not use the GUI thread but use a background thread instead or you application will become unresponsive as the save operation is in progress.