Question

我们期望为下面的枚举类提供什么样的值。困惑于＆lt;＆lt;运营商

public enum FrequencyEnum {

    DAILY       (1), 
    WEEKLY      (1 << 1), 
    BI_WEEKLY   (1 << 2), 
    MONTHLY     (1 << 3), 


    private short id;


    private FrequencyEnum(int id) {
        this.id = (short) id;
    }

    public short getId() {
        return id;
    }

    public void setId(short id) {
        this.id = id;
    }

    public static FrequencyEnum valueOf(short id) {
        for (FrequencyEnum status : FrequencyEnum.values()) {
            if (status.getId() == id) {
                return status;
            }
        }
        return null;
    }

}

Answer 1

<<是左移算子。在此上下文中，您将各种整数值传递给枚举构造函数（如kiruwka所述）。

请参阅：

http://en.wikipedia.org/wiki/Bitwise_operation http://docs.oracle.com/javase/tutorial/java/nutsandbolts/op3.html

java enum＆lt;＆lt;操作者

1 个答案: