It should be specified that the arrays returned by the following methods must not contain duplicates:
javax.sound.midi.MidiSystem:
  getMidiFileTypes()
  getMidiFileTypes(Sequence)
javax.sound.sampled.AudioSystem:
  getAudioFileTypes()
  getAudioFileTypes(AudioInputStream)
This is the current behaviour as implemented in response to #4883060. However, for developers being able to rely on this, it has to be specified explicitly, so that the behaviour is mandatory for third-party implementations, too.
###@###.### 2003-10-23
fixed