1. switch表达式(预览)

对switch语法糖进行了改进，使得switch代码编写更加简洁优雅。

enum DayOfWeek {
    MONDAY,
    TUESDAY,
    WEDNESDAY,
    THURSDAY,
    FRIDAY,
    SATURDAY,
    SUNDAY
}

public static void main(String[] args) {
    DayOfWeek dayOfWeek = DayOfWeek.MONDAY;
    // 多个case
    switch (dayOfWeek) {
        case MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY -> System.out.println("weekday");
        default -> System.out.println("weekend");
    }
    
    // switch表达式返回值
    int index = switch (dayOfWeek) {
        case MONDAY -> 1;
        case TUESDAY -> 4;
        default -> dayOfWeek.ordinal();
    };

    System.out.println(index);
}