How to speed up JTextArea?

If inputArea is a JTextArea and stringBuilder is a StringBuilder, you can

dispense with words and stringReader and just say// remove trailing new line

stringBuilder.deleteCharAt(stringBuilder.length() - 1);

// set JTextArea's content

ui.inputArea.setText(stringBuilder.toString());

pbrockway2a at 2007-7-15 0:44:38 >

Compare what you're doing with the following. I load a 2Mb file in 906ms.import java.awt.BorderLayout;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.io.BufferedReader;

import java.io.File;

import java.io.FileReader;

import java.util.Date;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JScrollPane;

import javax.swing.JTextArea;

import javax.swing.SwingUtilities;

public class TextAreaEg extends JFrame {

private JTextArea ta;

private static File[] loadMultipleFiles;

public TextAreaEg(String title) {

super(title);

ta = new JTextArea();

add(new JScrollPane(ta), BorderLayout.CENTER);

JButton but = new JButton("Click me!");

but.addActionListener(doTest);

add(but, BorderLayout.SOUTH);

}

private ActionListener doTest = new ActionListener() {

public void actionPerformed(ActionEvent evt) {

long start = new Date().getTime();

try {

StringBuilder stringBuilder = new StringBuilder();

for(File file: loadMultipleFiles) {

BufferedReader reader = new BufferedReader(new FileReader(file));

String line;

while((line = reader.readLine()) != null) {

stringBuilder.append(line);

stringBuilder.append("\n");

}

reader.close();

}

stringBuilder.deleteCharAt(stringBuilder.length() - 1);

ta.setText(stringBuilder.toString());

} catch(Exception e) {

e.printStackTrace();

}

long now = new Date().getTime();

setTitle("Took " + (now - start) + "ms");

}

};

public static void main(String[] args) {

loadMultipleFiles = new File[] {new File("test.txt")};

SwingUtilities.invokeLater(new Runnable() {

public void run() {createAndShowGUI();}

});

}

private static void createAndShowGUI() {

JFrame.setDefaultLookAndFeelDecorated(true);

TextAreaEg app = new TextAreaEg("How Long?");

app.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

app.pack();

app.setVisible(true);

}

}

Note: I have moved the line that appends a new line inside the while-loop where,

I guess, it belongs.

pbrockway2a at 2007-7-15 0:44:38 >

> Can I put that in my main, so it's not inside my GUI class?

I haven't seen your main() method, so I don't know! But I doubt that random

stuff can be pasted into it with any productive consequence. What I posted was

designed to merely be compiled, then run. How depends on whatever

operating system and (I suspect) IDE you are using.

Alternatively, compare the try-block I used in the doTest listener with what you

posted before. There are three differences: eliminating the substring() call, not

using a StringReader and appending a newline between every line that you

read. All three can be incorporated into your code.

pbrockway2a at 2007-7-15 0:44:38 >

My last post sort of "crossed" with yours.

> Wow, your program is a 1000x faster then mine... I'm not sure why mine is

> going so slow.

I guess you got what I posted to run.

OK, so now the hard bit starts. What I posted is at least an encouragement

(and a justification for what I said right at the start - that 100K isn't big).

(1) Have a look at the three things I mentioned in my last post and see if you

can incorporate them into your try-block. After having understood what they

do

(2) If you have no luck, you may have to post a compilable example of what

you are doing. Ie something others can reconstruct. Obviously nobody

wants 500 lines of code! Just a small example that shows the behaviour

you are trying to avoid. Creating a small example is not trivial and takes

time. However it can be very instructive and will help pinpoint (for you)

whatever it is that is causing the load to be so slow.

pbrockway2a at 2007-7-15 0:44:38 >

> It works! Thank you so much!

Great! You're welcome.

> Why does that make such a big difference?

The contents of a JTextArea can change (obviously). Behind the scenes this

means that there must be some mechanism for allowing inserts and

deletes without having to move huge amounts of data around.

One approach would be to keep the data in a linked list of smallish

"chunks". That way an insert or delete would only involve the particular

chunk that the data is in. I think (but am too lazy to look up) that the Swing

text components do some such thing, and that the actual strategy used can

be changed. In any case having a H - U - G - E string with no newlines

upsets this mechanism.

kajbj is right about not using gc() ... that was change number 4 I made to

your try-block. Basically the rule about gc() is just "don't".

pbrockway2a at 2007-7-21 11:23:14 >