Android Installation (unique ID per install)

Installataion.java

public class Installation {

    private static String sID;
    private static final String INSTALLATION = "INSTALLATION";

    // Usage: Just call Installation.id(this) from Application class onCreate and store in "session" (whatever you use for small temp in mem). 
    public synchronized static String id(Context context) {
        if (Installation.sID == null) {
            File installation = new File(context.getFilesDir(), Installation.INSTALLATION);
            try {
                if (!installation.exists()) {
                    Installation.writeInstallationFile(installation);
                }
                Installation.sID = Installation.readInstallationFile(installation);
            } catch (Exception e) {
                // fail fast
                throw new RuntimeException(e);
            }
        }
        return Installation.sID;
    }

    private static String readInstallationFile(File installation) throws IOException {
        RandomAccessFile f = new RandomAccessFile(installation, "r");
        byte[] bytes = new byte[(int) f.length()];
        f.readFully(bytes);
        f.close();
        return new String(bytes);
    }

    private static void writeInstallationFile(File installation) throws IOException {
        FileOutputStream out = new FileOutputStream(installation);
        String id = UUID.randomUUID().toString();
        out.write(id.getBytes());
        out.close();
    }
}