Question

I have a chat like desktop java swing app, where i keep getting String type data. Eventually the String variable keeps growing larger and larger.

1) Is it wise idea to keep the large variable in memory and only when the logging is finished save this to disk.

2) If not, then should i continue saving everytime i get a new string (of length about 30-40).

How should i go about optimizing such a desgin?

Answer 1

I would use a BufferedWriter, like PrintWriter. This will buffer the data for you and write every 8 KB (actually every 8192 characters). If you want to write more often you can use flush() or a smaller buffer.

PrintWriter pw = new PrintWriter("my.log");

// will actually write to the OS, 5 times. (1000 * 40 / 8192)
for(int i = 0; i < 1000; i++) {
   pw.printf("%39d%n", i); // a 40 character number.
}

pw.flush();

or you can use

pw.println(lineOfText);

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BTW: If you want to know what a really huge file looks like 😉 This example writes an 8 TB file http://vanillajava.blogspot.com/2011/12/using-memory-mapped-file-for-huge.html