core/src/in/srain/cube/image/ImageTask.java
public static String joinSizeTagToKey(String key, String tag) {
        return new StringBuilder(key).append(SIZE_SP).append(tag).toString();
    }
public static String joinSizeTagToKey(String key, String tag) {
        return new StringBuilder(key).append(SIZE_SP).append(tag).toString();
    }
Join the tag with the key.

@param key
@param tag
@return "$key" + "_" + "$tag"