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POProgress bar updater using up CPU
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copied!<p>I want to keep my user informed of the progress of an I/O operation. At the moment I've got an inner class that I kick off before I start my I/O and stop after it's done. It looks like this:</p> <pre><code>class ProgressUpdater implements Runnable { private Thread thread; private long last = 0; private boolean update = true; private long size; public ProgressUpdater(long size) { this.size = size; thread = new Thread(this); } @Override public void run() { while (update) { if (position > last) { last = position; double progress = (double) position / (double) size * 100d; parent.setProgress((int) progress); } } } public void start() { thread.start(); } public void stop() { update = false; parent.setProgress(100); } } </code></pre> <p><code>parent</code> is my reference to my UI and <code>position</code> is a field in my outer class that represents how far in the I/O we have progressed. I set progress to 100% when stopping because sometimes the I/O finishes and stops my updater before it can finish updating the previous increment. That just ensures it's at 100%.</p> <p>At the moment, this works, and I use it like this:</p> <pre><code>ProgressUpdater updater = new ProgressUpdater(file.length()); updater.start(); //do I/O //... updater.stop(); </code></pre> <p>The problem is that the loop eats CPU pretty badly. I tried throwing a lock (with a wait/notify) in there but I don't know what I'm doing when it comes to using wait/notify so it just hung my thread. What can I do to stop it from using so many CPU cycles?</p>

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