带返回值的switch中为什么default放最前面不需要返回值而放最后面就需要？

Question

public class RandomInstrumentGenerator {
    private Random rand = new Random();
    public Instrument next() {
        switch (rand.nextInt(6)) {
            case 0:
                return new Wind(); // return会直接跳出循环，不需要break
            case 1:
                return new Percussion();
            case 2:
                return new Stringed();
            case 3:
                return new Brass();
            case 4:
                return new Woodwind();
            case 5:
                return new Piano();
            default:
        }
    }
}

public class RandomInstrumentGenerator {
    private Random rand = new Random();
    public Instrument next() {
        switch (rand.nextInt(6)) {
            default:
            case 0:
                return new Wind(); // return会直接跳出循环，不需要break
            case 1:
                return new Percussion();
            case 2:
                return new Stringed();
            case 3:
                return new Brass();
            case 4:
                return new Woodwind();
            case 5:
                return new Piano();
        }
    }
}

当default放最后时还会报错：  Missing return statement

 

Answer 1

放前面由于没有break，所以会继续往下执行case 0的return

放最后没有return可执行