public static Part createFormData(String name, @Nullable String filename, RequestBody body) { if (name == null) { throw new NullPointerException("name == null"); } StringBuilder disposition = new StringBuilder("form-data; name="); appendQuotedString(disposition, name); if (filename != null) { disposition.append("; filename="); appendQuotedString(disposition, filename); } Headers headers = new Headers.Builder() .addUnsafeNonAscii("Content-Disposition", disposition.toString()) .build(); return create(headers, body); }