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copied!<p>As you see below, the performance of the date processing only is relevant when you look at <em>millions</em> of iterations. Instead, you should choose a solution that is easy to read and maintain.</p> <p>Although you could use <code>SimpleDateFormat</code>, it is not reentrant so should be avoided. The best solution is to use the great Joda time classes:</p> <pre><code>private static final DateTimeFormatter DATE_FORMATTER = new DateTimeFormatterBuilder() .appendYear(4,4).appendMonthOfYear(2).appendDayOfMonth(2).toFormatter(); ... Date date = DATE_FORMATTER.parseDateTime(dateOfBirth).toDate(); </code></pre> <hr> <p>If we are talking about your math functions, the first thing to point out is that there were bugs in your math code that I've fixed. <em>That's</em> the problem with doing by hand. That said, the ones that process the string once will be the fastest. A quick test run shows that:</p> <pre><code>year = Integer.parseInt(dateString.substring(0, 4)); month = Integer.parseInt(dateString.substring(4, 6)); day = Integer.parseInt(dateString.substring(6)); </code></pre> <p>Takes ~800ms while:</p> <pre><code>int date = Integer.parseInt(dateString); year = date / 10000; month = (date % 10000) / 100; day = date % 100; total += year + month + day; </code></pre> <p>Takes ~400ms.</p> <p><strong>However ... again...</strong> you need to take into account that this is after <strong>10 million</strong> iterations. This is a perfect example of premature optimization. I'd choose the one that is the most readable and the easiest to maintain. That's why the Joda time answer is the best. </p>

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