code: private static byte[] generateSeed() {
          try {
              ByteArrayOutputStream seedBuffer = new ByteArrayOutputStream();
              DataOutputStream seedBufferOut =
                      new DataOutputStream(seedBuffer);
              seedBufferOut.writeLong(System.currentTimeMillis());
              seedBufferOut.writeLong(System.nanoTime());
              seedBufferOut.writeInt(Process.myPid());
              seedBufferOut.writeInt(Process.myUid());
              seedBufferOut.write(BUILD_FINGERPRINT_AND_DEVICE_SERIAL);
              seedBufferOut.close();
              return seedBuffer.toByteArray();
          } catch (IOException e) {
              throw new SecurityException("Failed to generate seed", e);
          }
      }
docs: Generates a device- and invocation-specific seed to be mixed into the
  Linux PRNG.