libgdx/libgdx · error · IllegalArgumentException

extension cannot be null.

Error message

extension cannot be null.

What it means

Argument validation in OpenALLwjgl3Audio.registerSound: the extension key used for the sound-factory map cannot be null. Registering a supplier under a null key would make the map unusable for extension lookup, so it is rejected with IllegalArgumentException.

Source

Thrown at backends/gdx-backend-lwjgl3/src/com/badlogic/gdx/backends/lwjgl3/audio/OpenALLwjgl3Audio.java:180

						// Update last available devices
						lastAvailableDevices = currentDevices;
					}
					try {
						Thread.sleep(1000);
					} catch (InterruptedException ignored) {
						return;
					}
				}
			}
		});
		observerThread.setDaemon(true);
		observerThread.start();

		recentSounds = new OpenALSound[simultaneousSources];
	}

	public void registerSound (String extension, BiFunction<OpenALLwjgl3Audio, FileHandle, OpenALSound> soundSupplier) {
		if (extension == null) throw new IllegalArgumentException("extension cannot be null.");
		if (soundSupplier == null) throw new IllegalArgumentException("soundClass cannot be null.");
		extensionToSoundClass.put(extension, soundSupplier);
	}

	public void registerMusic (String extension, BiFunction<OpenALLwjgl3Audio, FileHandle, OpenALMusic> soundSupplier) {
		if (extension == null) throw new IllegalArgumentException("extension cannot be null.");
		if (soundSupplier == null) throw new IllegalArgumentException("musicClass cannot be null.");
		extensionToMusicClass.put(extension, soundSupplier);
	}

	public OpenALSound newSound (FileHandle file) {
		String extension = file.extension().toLowerCase();
		return newSound(file, extension);
	}

	public OpenALSound newSound (FileHandle file, String extension) {
		if (file == null) throw new IllegalArgumentException("file cannot be null.");
		BiFunction<OpenALLwjgl3Audio, FileHandle, OpenALSound> soundSupplier = extensionToSoundClass.get(extension);

View on GitHub (pinned to 97f4086187)

Solutions

1. Pass a concrete lowercase extension literal such as "ogg" or "mp3".
2. If deriving from a filename, null/empty-check it before registering.
3. Verify which overload you called — registerSound vs registerMusic take the same first parameter.

Example fix

// before
String ext = config.get("soundExt"); // null when missing
audio.registerSound(ext, supplier);

// after
String ext = config.get("soundExt");
if (ext == null || ext.isEmpty()) throw new IllegalStateException("soundExt missing in config");
audio.registerSound(ext.toLowerCase(), supplier);

if (ext == null || ext.isEmpty()) throw new IllegalArgumentException("ext required");
audio.registerSound(ext.toLowerCase(), supplier);

When it happens

Trigger: Calling audio.registerSound(null, supplier), usually because the extension string was computed (e.g. file.extension() on a path with no dot, or from config) and came back null/blank.

Common situations: Plugin/mod systems registering codecs from config files, or dynamic extension derivation where a missing value flows through as null.

Related errors

• length cannot be < 0.
• file cannot be null.
• volume cannot be < 0: {}
• numSamples cannot be < 0.
• numSamples cannot be < 0.

AI-assisted analysis of libgdx/libgdx@97f4086187 (2026-08-14). Data as JSON: /api/errors/4f7d2aae7c23e2a4. Report an issue: GitHub.