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Groups > comp.lang.java.programmer > #38277

Re: how do you block the GUI repaints?

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On 2018-05-23 14:54, Eric Douglas wrote:
> On Tuesday, May 22, 2018 at 10:31:46 PM UTC-4, Daniele Futtorovic wrote:
>> Yes, seriously, it would. Have a look at the Javadoc
>> (<https://docs.oracle.com/javase/9/docs/api/java/io/RandomAccessFile.html>),
>> at the class definition, and search for usage examples if that's not enough.
>>
>> Of course, that class will only come in handy if and when you give up on
>> the absurd notion of loading multi-gig files into RAM just in order to
>> show a couple lines of it. But then it most likely /will/ come in
>> handy... unless you have variable-length character encodings in it, in
>> which case you'd probably have to index the file before. But still.
>>
> 
> That seems to work with the same code I mentioned, just putting this class in place of FileInputStream. 

Using the RandomAccessFile will allow you, for instance, to display just
the last page of the file without reading through all the previous data
(which would cause a delay).

> I'm not sure what you mean with the variable-length character encodings, 

I mean that if you have a fixed-length character encoding (say, ASCII or
UTF-16), you can compute the position of character N in the file (in
case of UTF-16, it would be at byte position N*2).

If you have variable-length encoding, you cannot do that. You would have
for instance to precompute the byte position of each line by doing a
pass on the whole file first; only after that could you page through it
(i.e., display line N to N+50).

> but on a related note how do I display characters in JTextArea?  I tried reading a little PDF with this logic into a byte[] array, passing that into a String constructor, passing that into the insert method and I get a lot of squares.

PDF is a binary file, not a text file. Everything I mentioned previously
was under the assumption that you were working with text files. If you
want to display a PDF, you'll likely be better off using a third-party
library (not sure those even exist for Java, but they may).

-- 
DF.

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how do you block the GUI repaints? Eric Douglas <e.d.programmer@gmail.com> - 2018-05-22 10:59 -0700
  Re: how do you block the GUI repaints? Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2018-05-22 13:22 -0500
    Re: how do you block the GUI repaints? Eric Douglas <e.d.programmer@gmail.com> - 2018-05-22 13:00 -0700
      Re: how do you block the GUI repaints? Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-05-22 16:29 -0400
        Re: how do you block the GUI repaints? Eric Douglas <e.d.programmer@gmail.com> - 2018-05-22 13:51 -0700
          Re: how do you block the GUI repaints? Martin Gregorie <martin@mydomain.invalid> - 2018-05-22 21:41 +0000
          Re: how do you block the GUI repaints? Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-05-22 18:03 -0400
            Re: how do you block the GUI repaints? Andreas Leitgeb <avl@logic.at> - 2018-05-22 22:22 +0000
              Re: how do you block the GUI repaints? Eric Douglas <e.d.programmer@gmail.com> - 2018-05-23 07:55 -0700
                Re: how do you block the GUI repaints? Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-05-23 11:06 -0400
                Re: how do you block the GUI repaints? Eric Douglas <e.d.programmer@gmail.com> - 2018-05-23 08:19 -0700
  Re: how do you block the GUI repaints? Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-05-22 14:43 -0400
    Re: how do you block the GUI repaints? Eric Douglas <e.d.programmer@gmail.com> - 2018-05-22 13:20 -0700
      Re: how do you block the GUI repaints? Daniele Futtorovic <da.futt.news@laposte.net> - 2018-05-22 22:47 +0200
        Re: how do you block the GUI repaints? Eric Douglas <e.d.programmer@gmail.com> - 2018-05-22 13:58 -0700
          Re: how do you block the GUI repaints? Daniele Futtorovic <da.futt.news@laposte.net> - 2018-05-23 04:30 +0200
            Re: how do you block the GUI repaints? Eric Douglas <e.d.programmer@gmail.com> - 2018-05-23 05:54 -0700
              Re: how do you block the GUI repaints? Daniele Futtorovic <da.futt.news@laposte.net> - 2018-05-23 15:58 +0200
                Re: how do you block the GUI repaints? Eric Douglas <e.d.programmer@gmail.com> - 2018-05-23 07:26 -0700
                Re: how do you block the GUI repaints? Daniele Futtorovic <da.futt.news@laposte.net> - 2018-05-23 16:30 +0200
                Re: how do you block the GUI repaints? Eric Douglas <e.d.programmer@gmail.com> - 2018-05-23 07:48 -0700
                Re: how do you block the GUI repaints? Daniele Futtorovic <da.futt.news@laposte.net> - 2018-05-23 18:46 +0200
                Re: how do you block the GUI repaints? Eric Douglas <e.d.programmer@gmail.com> - 2018-05-23 10:51 -0700
                Re: how do you block the GUI repaints? Daniele Futtorovic <da.futt.news@laposte.net> - 2018-05-23 22:35 +0200

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