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POOptimum time to perform an operation: within, or after loop
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copied!<p>I am reading a file to parse later on. The file is not likely to exceed an MB in size, so this is perhaps not a crucial question for me at this stage. But for best practise reasons, I'd like to know when is the optimum time to perform an operation.</p> <p>Example:</p> <p>Using a method I've pasted from <a href="http://www.dzone.com/snippets/java-read-file-string" rel="nofollow">http://www.dzone.com/snippets/java-read-file-string</a>, I am reading a buffer into a string. I would now like to remove all whitespace. My method is currently this:</p> <pre><code>private String listRaw; public boolean readList(String filePath) throws java.io.IOException { StringBuffer fileData = new StringBuffer(1024); BufferedReader reader = new BufferedReader( new FileReader(filePath)); char[] buf = new char[1024]; int numRead=0; while((numRead=reader.read(buf)) != -1){ String readData = String.valueOf(buf, 0, numRead); fileData.append(readData); buf = new char[1024]; } reader.close(); listRaw = fileData.toString().replaceAll("\\s",""); return true; } </code></pre> <p>So, I remove all whitespace from the string at the time I store it - in it's entirety - to a class variable.</p> <p>To me, this means less processing but more memory usage. Would I be better off applying the <code>replaceAll()</code> operation on the <code>readData</code> variable as I append it to <code>fileData</code> for best practise reasons? Using more processing but avoiding passing superfluous whitespace around.</p> <p>I imagine this has little impact for a small file like the one I am working on, but what if it's a 200MB log file?</p> <p>Is it entirely case-dependant, or is there a consensus I'd do better to follow?</p> <hr> <p>Thanks for the input everybody. I'm sure you've helped to aim my mindset in the right direction for writing Java.</p> <p>I've updated my code to take into consideration the points raised. Including the suggestion by Don Roby that at some point, I may want to keep spaces. Hopefully things read better now!</p> <pre><code>private String listRaw; public boolean readList(String filePath) throws java.io.IOException { StringBuilder fileData = new StringBuilder(51200); BufferedReader reader = new BufferedReader(new FileReader(filePath)); char[] buf = new char[51200]; boolean spaced = false; while(reader.read(buf) != -1){ for(int i=0;i<buf.length;i++) { char c = buf[i]; if (c != '\t' && c != '\r' && c != '\n') { if (c == ' ') { if (spaced) { continue; } spaced = true; } else { spaced = false; } fileData.append(c); } } } reader.close(); listRaw = fileData.toString().trim(); return true; } </code></pre>

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