static void checkInitialization() {
        if (!sIsInitialized) {
            System.out.println(Log.getStackTraceString(new IllegalStateException("Do you forget to initialize XLog?")));
            // Init by default.
            init();
        }
    }
Throw an IllegalStateException if not initialized.
android/android_framework/base/src/main/java/com/elvishew/xlog/XLog.java