skylot/jadx · error · JadxRuntimeException

String is too long:

Error message

String is too long: 

What it means

Thrown by ClsSet.writeString() when a string being serialized to the .clst file exceeds 254 bytes in STRING_CHARSET encoding. The binary format uses a single unsigned byte for the length prefix (writeUnsignedByte), so it cannot represent lengths of 255 or greater. This is a format limitation, not a logic error.

Source

Thrown at jadx-core/src/main/java/jadx/core/clsp/ClsSet.java:455

				return classes[in.readInt()].getClsType();

			case ARRAY:
				return ArgType.array(Objects.requireNonNull(readArgType(in)));

			case PRIMITIVE:
				char shortName = (char) in.readByte();
				return ArgType.parse(shortName);

			default:
				throw new JadxRuntimeException("Unsupported Arg Type: " + ordinal);
		}
	}

	private static void writeString(DataOutputStream out, String name) throws IOException {
		byte[] bytes = name.getBytes(STRING_CHARSET);
		int len = bytes.length;
		if (len >= 0xFF) {
			throw new JadxRuntimeException("String is too long: " + name);
		}
		writeUnsignedByte(out, bytes.length);
		out.write(bytes);
	}

	private static String readString(DataInputStream in) throws IOException {
		int len = readUnsignedByte(in);
		return readString(in, len);
	}

	private static String readString(DataInputStream in, int len) throws IOException {
		byte[] bytes = new byte[len];
		int count = in.read(bytes);
		while (count != len) {
			int res = in.read(bytes, count, len - count);
			if (res == -1) {
				throw new IOException("String read error");
			} else {

View on GitHub (pinned to e738a26571)

Solutions

1. Shorten or rename the offending class/type string so its encoded length stays under 255 bytes.
2. If you control the format, extend the length encoding to use two bytes (modify writeString/readString and writeUnsignedByte) — but this is a breaking format change requiring all readers to be updated.
3. Exclude the offending classes from the ClsSet export and document the 254-byte name limit.

Example fix

// before
//   writeString uses single-byte length, fails at >= 255 bytes
// after: extend to unsigned short (breaking format change)
//   private static void writeString(DataOutputStream out, String name) {
//       byte[] bytes = name.getBytes(STRING_CHARSET);
//       out.writeShort(bytes.length);
//       out.write(bytes);
//   }

// Before exporting a ClsSet, validate string lengths
private static void validateStringForExport(String name) {
    byte[] bytes = name.getBytes(STRING_CHARSET);
    if (bytes.length >= 0xFF) {
        throw new IllegalArgumentException(
            "Class/type name too long for .clst format (max 254 bytes): " + name);
    }
}
// Call before ClsSet.save() for each class name and type variable

try {
    clsSet.save(outputStream);
} catch (JadxRuntimeException e) {
    if (e.getMessage().startsWith("String is too long")) {
        // Identify and shorten the offending name
        logger.error("Class name exceeds 254-byte format limit. Rename or exclude it.", e);
    }
    throw e;
}

When it happens

Trigger: Calling ClsSet.save() or any codepath that writes a class name, type variable name, or other string whose encoded byte length is >= 255. Most common with extremely long obfuscated class names or deeply nested generic type signatures.

Common situations: Generating a custom .clst classpath that includes heavily obfuscated app classes with very long names. Processing a classpath with generated/templated class names that exceed the byte limit.

Related errors

• Unsupported Arg Type:
• Unsigned byte value is too big:
• Cannot save type:
• Wrong jadx class set header
• Wrong jadx class set version, got:

AI-assisted analysis of skylot/jadx@e738a26571 (2026-08-14). Data as JSON: /api/errors/000ea1dc9af44743. Report an issue: GitHub.