jodd-core/src/main/java/jodd/net/MimeTypes.java
public static String[] findExtensionsByMimeTypes(String mimeType, final boolean useWildcard) {
		final ArrayList<String> extensions = new ArrayList<>();

		mimeType = mimeType.toLowerCase();
		final String[] mimeTypes = StringUtil.splitc(mimeType, ", ");

		for (final Map.Entry<String, String> entry : MIME_TYPE_MAP.entrySet()) {
			final String entryExtension = entry.getKey();
			final String entryMimeType = entry.getValue().toLowerCase();

			final int matchResult = useWildcard ?
					Wildcard.matchOne(entryMimeType, mimeTypes) :
					StringUtil.equalsOne(entryMimeType, mimeTypes);

			if (matchResult != -1) {
				extensions.add(entryExtension);
			}
		}

		if (extensions.isEmpty()) {
			return StringPool.EMPTY_ARRAY;
		}

		return extensions.toArray(new String[0]);
	}
public static String[] findExtensionsByMimeTypes(String mimeType, final boolean useWildcard) {
		final ArrayList<String> extensions = new ArrayList<>();

		mimeType = mimeType.toLowerCase();
		final String[] mimeTypes = StringUtil.splitc(mimeType, ", ");

		for (final Map.Entry<String, String> entry : MIME_TYPE_MAP.entrySet()) {
			final String entryExtension = entry.getKey();
			final String entryMimeType = entry.getValue().toLowerCase();

			final int matchResult = useWildcard ?
					Wildcard.matchOne(entryMimeType, mimeTypes) :
					StringUtil.equalsOne(entryMimeType, mimeTypes);

			if (matchResult != -1) {
				extensions.add(entryExtension);
			}
		}

		if (extensions.isEmpty()) {
			return StringPool.EMPTY_ARRAY;
		}

		return extensions.toArray(new String[0]);
	}
Finds all extensions that belong to given mime type(s).
If wildcard mode is on, provided mime type is wildcard pattern.
@param mimeType list of mime types, separated by comma
@param useWildcard if set, mime types are wildcard patterns