public synchronized static SafeKeyGenerator getInstance() {
        if (safeKeyGenerator == null) {
            safeKeyGenerator = new SafeKeyGenerator();
        }
        return safeKeyGenerator;
    }
A class that generates and caches safe and unique string file names from {@link Key}s.
core/src/main/java/com/bumptech/glide/load/engine/cache/SafeKeyGenerator.java