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copied!<p>I had a look at three options:</p> <ol> <li>Using <code>DataOutputStream</code>;</li> <li>Using <code>ObjectOutputStream</code> (for <code>Serializable</code> objects, which <code>int[]</code> is); and</li> <li>Using <code>FileChannel</code>.</li> </ol> <p>The results are</p> <pre><code>DataOutputStream wrote 1,000,000 ints in 3,159.716 ms ObjectOutputStream wrote 1,000,000 ints in 295.602 ms FileChannel wrote 1,000,000 ints in 110.094 ms </code></pre> <p>So the NIO version is the fastest. It also has the advantage of allowing edits, meaning you can easily change one int whereas the <code>ObjectOutputStream</code> would require reading the entire array, modifying it and writing it out to file.</p> <p>Code follows:</p> <pre><code>private static final int NUM_INTS = 1000000; interface IntWriter { void write(int[] ints); } public static void main(String[] args) { int[] ints = new int[NUM_INTS]; Random r = new Random(); for (int i=0; i<NUM_INTS; i++) { ints[i] = r.nextInt(); } time("DataOutputStream", new IntWriter() { public void write(int[] ints) { storeDO(ints); } }, ints); time("ObjectOutputStream", new IntWriter() { public void write(int[] ints) { storeOO(ints); } }, ints); time("FileChannel", new IntWriter() { public void write(int[] ints) { storeFC(ints); } }, ints); } private static void time(String name, IntWriter writer, int[] ints) { long start = System.nanoTime(); writer.write(ints); long end = System.nanoTime(); double ms = (end - start) / 1000000d; System.out.printf("%s wrote %,d ints in %,.3f ms%n", name, ints.length, ms); } private static void storeOO(int[] ints) { ObjectOutputStream out = null; try { out = new ObjectOutputStream(new FileOutputStream("object.out")); out.writeObject(ints); } catch (IOException e) { throw new RuntimeException(e); } finally { safeClose(out); } } private static void storeDO(int[] ints) { DataOutputStream out = null; try { out = new DataOutputStream(new FileOutputStream("data.out")); for (int anInt : ints) { out.write(anInt); } } catch (IOException e) { throw new RuntimeException(e); } finally { safeClose(out); } } private static void storeFC(int[] ints) { FileOutputStream out = null; try { out = new FileOutputStream("fc.out"); FileChannel file = out.getChannel(); ByteBuffer buf = file.map(FileChannel.MapMode.READ_WRITE, 0, 4 * ints.length); for (int i : ints) { buf.putInt(i); } file.close(); } catch (IOException e) { throw new RuntimeException(e); } finally { safeClose(out); } } private static void safeClose(OutputStream out) { try { if (out != null) { out.close(); } } catch (IOException e) { // do nothing } } </code></pre>

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