3

如何在 java <5.0 .. 中模拟枚举类型的类？？

public final class Week {

    private static final Day[] _week = {Day.MONDAY, Day.TUESDAY, Day.WEDNESDAY, Day.THURSDAY, Day.FRIDAY, Day.SATURDAY, Day.SUNDAY};

    public static Day getDayOfWeek(final int index) {
        if (index >= 1 && index <= 7) {
            return _week[index - 1];
        }
        throw new IndexOutOfBoundsException("Invalid index [1..7]");
    }

    public static final class Day {
        public static final Day MONDAY = new Day(1, "Monday");
        public static final Day TUESDAY = new Day(2, "Tuesday");
        public static final Day WEDNESDAY = new Day(3, "Wednesday");
        public static final Day THURSDAY = new Day(4, "Thursday");
        public static final Day FRIDAY = new Day(5, "Friday");
        public static final Day SATURDAY = new Day(6, "Saturday");
        public static final Day SUNDAY = new Day(7, "Sunday");

        private int _value;
        private String _name;

        private Day(final int value, final String name) {
            _value = value;
            _name = name;
        }

        /* (non-Javadoc)
         * @see java.lang.Object#toString()
         */
        public String toString() {
            return "[Day] " + _name;
        }

        /* (non-Javadoc)
         * @see java.lang.String#equals(java.lang.Object)
         */
        public boolean equals(Object anObject) {
            Day d = (Day)anObject;
            return _value == d._value;
        }
    }

    public static void main(String[] agrs) {
         System.out.println(Week.getDayOfWeek(2));
    }
}
4

4 回答 4

5

使用有效的 java.lang 中描述的类型安全枚举。这是Joshua Blochs 文章给出的一个例子：

// The typesafe enum pattern
public class Suit {
    private final String name;

    private Suit(String name) { this.name = name; }

    public String toString()  { return name; }

    public static final Suit CLUBS =
        new Suit("clubs");
    public static final Suit DIAMONDS =
        new Suit("diamonds");
    public static final Suit HEARTS =
        new Suit("hearts");
    public static final Suit SPADES =
        new Suit("spades");
}

如果您希望您的类型安全枚举是Serializable，请记住通过该readResolve方法控制重建。

于 2010-08-19T09:43:46.450 回答
4

Joshua Bloch 很久以前写了一篇文章来解释它。

于 2010-08-19T09:42:46.567 回答
0

Joshua Bloch 在他的“Effective Java”的第一版中向您展示了如何。我要上班，所以我现在不能输入详细信息。更多关注。

于 2010-08-19T09:41:40.733 回答
0

Krock 和 Riduidel 建议的解决方案非常简洁，但是 AFAIKswitch-case声明是不可能的，因为它仅适用于可转换的int值和enum常量。 switch-case组合是一个很好的功能，比一堆ifs 更具可读性（顺便说一句：无论如何switch-case都会被编译为一堆ifs，对吗？）。所以，为了完成所讨论的模式，有人可以告诉是否有一种快速的方法来启用这个模式并允许功能switch-case？为其添加int属性和吸气剂似乎是最简单的方法，但它是最优的吗？

于 2010-08-19T13:47:11.007 回答