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copied!<p><s>Just wondering why can't you use <code>java.util.BitSet;</code> </s></p> <p>Basically what you can do, is to read the whole data as <code>byte[]</code>, convert it to binary in <code>string</code> format and use string utilities like <code>.substring()</code> to do the work. This will also work <code>bit sequences > 16</code>. </p> <p>Lets say you have 3 bytes: <code>1, 2, 3</code> and you want to extract bit sequence from 5th to 16th bit.</p> <p><strong>Number Binary</strong></p> <pre><code>1 00000001 2 00000010 3 00000011 </code></pre> <p><strong>Code example:</strong></p> <pre><code>public static String getRealBinary(byte[] input){ StringBuilder sb = new StringBuilder(); for (byte c : input) { for (int n = 128; n > 0; n >>= 1){ if ((c & n) == 0) sb.append('0'); else sb.append('1'); } } return sb.toString(); } public static void main(String[] args) { byte bytes[] = new byte[]{1,2,3}; String sbytes = getRealBinary(bytes); System.out.println(sbytes); System.out.println(sbytes.substring(5,16)); } </code></pre> <p><strong>Output:</strong></p> <pre><code>000000010000001000000011 00100000010 </code></pre> <p><strong>Speed:</strong></p> <p>I did a testrun for <strong>1m</strong> times and on my computer it took <strong>0.995s</strong>, so its reasonably very fast:</p> <p>Code to repeat the test yourself:</p> <pre><code>public static void main(String[] args) { Random r = new Random(); byte bytes[] = new byte[4]; long start, time, total=0; for (int i = 0; i < 1000000; i++) { r.nextBytes(bytes); start = System.currentTimeMillis(); getRealBinary(bytes).substring(5,16); time = System.currentTimeMillis() - start; total+=time; } System.out.println("It took " +total + "ms"); } </code></pre>

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