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  1. PO
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    <p>Array copy is a rather unexpensive operation. It is done on a very basic level (its a java native static method) and you are not yet in the range where the performance becomes really important. </p> <p>In your example you copy approx 12000 times an array of size 150000 (on average). This does not take much time. I tested it here on my laptop and it took less than 500 ms.</p> <p><strong>Update</strong> I used the following code to measure on my laptop (Intel P8400)</p> <pre><code>import java.util.Random; public class PerformanceArrayCopy { public static void main(String[] args) { int[] lengths = new int[] { 10000, 50000, 125000, 250000 }; int[] loops = new int[] { 1000, 5000, 10000, 20000 }; for (int length : lengths) { for (int loop : loops) { Object[] list1 = new Object[length]; Object[] list2 = new Object[length]; for (int k = 0; k &lt; 100; k++) { System.arraycopy(list1, 0, list2, 0, list1.length); } int[] len = new int[loop]; int[] ofs = new int[loop]; Random rnd = new Random(); for (int k = 0; k &lt; loop; k++) { len[k] = rnd.nextInt(length); ofs[k] = rnd.nextInt(length - len[k]); } long n = System.nanoTime(); for (int k = 0; k &lt; loop; k++) { System.arraycopy(list1, ofs[k], list2, ofs[k], len[k]); } n = System.nanoTime() - n; System.out.print("length: " + length); System.out.print("\tloop: " + loop); System.out.print("\truntime [ms]: " + n / 1000000); System.out.println(); } } } } </code></pre> <p>Some results:</p> <pre><code>length: 10000 loop: 10000 runtime [ms]: 47 length: 50000 loop: 10000 runtime [ms]: 228 length: 125000 loop: 10000 runtime [ms]: 575 length: 250000 loop: 10000 runtime [ms]: 1198 </code></pre>
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    1. POWhy does Java's ArrayList's remove function seem to cost so little?
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    1. USHoward
    1. USHoward
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      1. VTUpMod
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    1. CO+1: Would be useful if you could add the test code to your answer (assuming it's short), and some basic specs for your platform.
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      1. USOliver Charlesworth
    2. CO@Oli Charlesworth: I'd like to but the system currently does no allow me to edit. Strange...
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      1. USHoward
    3. CO+1 for writing a simple benchmark while still avoiding the usual pitfalls. Although if he doesn't need random access an iterator over a linked list should be faster - that is if he uses the iterators remove which seems to be the real problem here.
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