Add a line at a time to a String

Question

I have this program that lets you open a file and it reads it in to a JTextArea all at once using the following code:

 try{
    String fileContents = new Scanner(new File(fileName)).useDelimiter("\\Z").next();
  }catch(FileNotFoundException ex){
    ex.printStackTrace();
  }

  myTextArea.setText(fileContents);

and this works. But my question is how can I read this into my fileContents string and still have it add in the line breaks every time I get a new-line character?

Here is what I have, but this puts it all in one line in my textArea:

 try{
Scanner contentsTextFile = new Scanner(new File(fileName));
while(contentsTextFile.hasNext()){
    fileContents = contentsTextFile.useDelimiter("\r\n|\n").nextLine(); 
    }

}catch(FileNotFoundException ex){
    ex.printStackTrace();
}

   myTextArea.setText(fileContents);

What I would like to see is this line of text get a new line using a delimiter that only reads one line at a time instead of the entire file.

Can someone help?

score 3 · Answer 1 · answered May 16 '13 at 13:34

3

The easiest way is to use JTextComponent.read(Reader,Object) which:

Initializes from a stream. This creates a model of the type appropriate for the component and initializes the model from the stream. By default this will load the model as plain text. Previous contents of the model are discarded.

answered May 16 '13 at 13:34

Andrew Thompson

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I am not sure i understand what you are telling me. Can't i just read a line into a string at a time and concatenate it onto what the string already contains and supply each new concatenation with a newline character? – kandroidj May 16 '13 at 14:09
Try it and see what it does. – Andrew Thompson May 16 '13 at 14:10
Let me try this and i will get back to you. Thanks in advance – kandroidj May 16 '13 at 14:12
Also consider the `append()` method of `JTextArea`. – trashgod May 16 '13 at 19:32

score 3 · Accepted Answer · edited May 23 '17 at 12:12

3

You can read a file line-by-line using a BufferedReader and use the append() method of JTextArea for each line read. For convenience, wrap the JTextArea in a suitably sized JScrollPane, as shown here. If you anticipate any latency, use a SwingWorker to read in the background, and call append() in process().

BufferedReader in = new BufferedReader(new FileReader(fileName));
String s;
while ((s = in.readLine()) != null) {
    myTextArea.append(s + "\n");
}

edited May 23 '17 at 12:12

Community

1
1

answered May 16 '13 at 19:29

trashgod

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yeah this is what i decided i would do. I get the file contents using the `FileReader` and `BufferedReader` then i append them one at a time to the `JTextArea` using `myTextArea.append(contents);` – kandroidj May 16 '13 at 19:35
1

+1 but JTextComponent.read/write accepting separators in file (both directions I/O) – mKorbel May 16 '13 at 20:02
2

@mKorbel: Agree for undivided operation on `Document`. Anything but `Scanner`! :-) – trashgod May 16 '13 at 20:22

Add a line at a time to a String

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