question: public AppendableSequenceAudioInputStream ( AudioFormat audioFormat , Collection < AudioInputStream > audioInputStreams ) { super ( audioFormat , audioInputStreams != null ? audioInputStreams : Arrays . asList ( new AudioInputStream [ 0 ] ) ) ; }
target:  Create a sequence audio input stream to which more AudioInputStreams can be appended after creation. When the currently available audio input streams have been read, calls to read() will block until new audio data is appended or doneAppending() is called. After doneAppending() is called, read() will return -1 when running out of data.