public static boolean isAbsoluteUri(@Nullable String maybeUri) {
        if (maybeUri == null) {
            return false;
        }
        final int firstColonIdx = maybeUri.indexOf(':');
        if (firstColonIdx <= 0 || firstColonIdx + 3 >= maybeUri.length()) {
            return false;
        }
        final int firstSlashIdx = maybeUri.indexOf('/');
        if (firstSlashIdx <= 0 || firstSlashIdx < firstColonIdx) {
            return false;
        }

        return maybeUri.charAt(firstColonIdx + 1) == '/' && maybeUri.charAt(firstColonIdx + 2) == '/';
    }
Returns {@code true} if the specified {@code path} is an absolute {@code URI}.
core/src/main/java/com/linecorp/armeria/internal/common/ArmeriaHttpUtil.java