java - 此处不允许使用“无效”类型

Question

出现异常错误：- 此处不允许使用“void”类型

import javax.sound.midi.*;

 public class MiniMusicPlayer1 {
    public static void main(String[] args) {
            try {
                    Sequencer player = MidiSystem.getSequencer();
                    Sequence seq = new Sequence(Sequence.PPQ, 4);
                    Track track = seq.createTrack();
                    for (int i = 5; i < 61; i += 4) {
                            track.add(makeEvent(144, 1, i, 100, i));
                            track.add(makeEvent(128, 1, i, 100, i));
                    }

                            player.setSequence(seq);
                            player.setTempoInBPM(220);
                            player.start();



            } catch (Exception ex) {
                    System.out.println(ex.printStackTrace());
            }
    }

    public static MidiEvent makeEvent(int comd, int ch, int note, int vel,
                    int tick) {
            MidiEvent event = null;
            try
            {
                    ShortMessage a = new ShortMessage();
                    a.setMessage(comd, ch, note, vel);
                    event = new MidiEvent(a,tick);

            }
            catch(Exception e)
            {
                    System.out.println(e.getMessage());
            }
            return event;
    }

ankit@battlestar:/home/mount_150/Java$ javac MiniMusicPlayer1.java MiniMusicPlayer1.java:21: error: 'void' type not allowed here System.out.println(ex.printStackTrace()); ^

请帮忙。

Answer 1

您正在调用printStackTrace并将其 void 结果“传递”到println.

println需要打印一些东西：您只需要ex.printStackTrace().