Generate Entropy UID for Android

gistfile1.java

private static String generateUid() {
        // STEP 1: get time since Epoch.
        // OUTPUT: timestamp in millisecond (or finer) granularity.
        // RATIONALE: collision only when app is deployed at the exact same time.
        final String s1 = Long.valueOf((new Date()).getTime()).toString();

        // STEP 2: get an object reference.
        // OUTPUT: memory address or another distinguishable object property.
        // RATIONALE: very little probability for two runs to get the
        // same address (debatable when in a sandbox).
        final String s2 = (new Object()).toString();

        // STEP 3: sleep for a little time.
        // OUTPUT: time delta in _finer_ millisecond granularity.
        // RATIONALE: os fine timing granularity is not guaranteed
        // (debatable when dealing with real-time/hard real-time kernels).
        final long dat1 = System.nanoTime();
        try {
                Thread.sleep(256, 42);
        } catch (InterruptedException e) {
        
        }
        final long dat2 = System.nanoTime();
        final String s3 = Long.valueOf(dat2 - dat1).toString();

        // STEP 4: generate a random number.
        // OUTPUT: random integer.
        // RATIONALE: the pseudo-random generator may be the same, but there
        // is a slight chance that something might have changed in the
        // seed (may be a second passed in some cases).
        // Also, some systems (e.g. a JVM) have their own pseudo-random
        // generators that are "fed" with their own implementations,
        // narrowing the probability for same results.

        final String s4 = Integer.valueOf((int) (new Random(System.currentTimeMillis()).nextDouble() * 65535)).toString();

        final String s5 = Secure.ANDROID_ID;

        // The output string.
        final String sall = s1 + s2 + s3 + s4 + s5;

        // MD5 from output string.
        byte[] thedigest = null;
        try {
                final byte[] bytesOfMessage = sall.getBytes("UTF-8");
                final MessageDigest md = MessageDigest.getInstance("MD5");
                thedigest = md.digest(bytesOfMessage);
        } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
        } catch (NoSuchAlgorithmException e) {
                e.printStackTrace();
        }

        // RESULT.
        return new String(encodeHex(thedigest));
}