Java枚举常见7种用法("Java枚举的7种常用技巧详解")

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ithorizon 6个月前 (10-20) 阅读数 21 #后端开发

Java枚举的7种常用技巧详解

一、定义枚举类型

Java枚举类型是Java 5引入的一个特性，它允许开发者定义一组具有特定语义的常量集合。枚举类型通常用于即一组固定的、命名的常量集合，如星期、月份、方向等。


public enum Weekday {
    MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY
}

二、枚举类型的方法

枚举类型可以像普通类一样拥有属性和方法。下面是一个明了的示例，展示了怎样在枚举类型中定义方法和属性。


public enum Weekday {
    MONDAY(1), TUESDAY(2), WEDNESDAY(3), THURSDAY(4), FRIDAY(5), SATURDAY(6), SUNDAY(7);
    private int value;
    Weekday(int value) {
        this.value = value;
    }
    public int getValue() {
        return value;
    }
    public String getName() {
        return name();
    }
}

三、枚举类型的switch语句

Java枚举类型可以用于switch语句，这允许枚举类型在处理多选分支逻辑时更加方便。


public class EnumTest {
    public static void main(String[] args) {
        Weekday today = Weekday.FRIDAY;
        switch (today) {
            case MONDAY:
                System.out.println("Today is Monday");
                break;
            case TUESDAY:
                System.out.println("Today is Tuesday");
                break;
            case WEDNESDAY:
                System.out.println("Today is Wednesday");
                break;
            case THURSDAY:
                System.out.println("Today is Thursday");
                break;
            case FRIDAY:
                System.out.println("Today is Friday");
                break;
            case SATURDAY:
                System.out.println("Today is Saturday");
                break;
            case SUNDAY:
                System.out.println("Today is Sunday");
                break;
        }
    }
}

四、枚举类型的比较

枚举类型提供了equals()和compareTo()方法来比较枚举值。equals()方法用于检查两个枚举值是否相同，而compareTo()方法用于比较两个枚举值的顺序。


public class EnumTest {
    public static void main(String[] args) {
        Weekday today = Weekday.FRIDAY;
        Weekday tomorrow = Weekday.SATURDAY;
        if (today.equals(Weekday.FRIDAY)) {
            System.out.println("Today is Friday");
        }
        if (today.compareTo(tomorrow) < 0) {
            System.out.println("Today comes before tomorrow");
        }
    }
}

五、枚举类型的迭代

可以使用values()方法来获取枚举类型的所有值，并以数组的形式返回。这允许我们遍历枚举类型中的所有值。


public class EnumTest {
    public static void main(String[] args) {
        for (Weekday day : Weekday.values()) {
            System.out.println(day);
        }
    }
}

六、枚举类型与接口

枚举类型可以实现一个或多个接口。这允许枚举类型具有更多的灵活性，并且能够提供更多的功能。


public interface Greeting {
    void greet();
}
public enum Weekday implements Greeting {
    MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY;
    @Override
    public void greet() {
        System.out.println("Hello, this is a weekday!");
    }
}
public class EnumTest {
    public static void main(String[] args) {
        Weekday.FRIDAY.greet();
    }
}

七、枚举类型的高级用法

枚举类型可以拥有自己的构造器、方法和属性，这允许它们可以非常强劲和灵活。以下是一个更高级的示例，演示了怎样使用枚举类型来即一个操作系统的命令。


public enum OSCommand {
    LS {
        public void execute() {
            System.out.println("Executing 'ls' command");
        }
    },
    pwd {
        public void execute() {
            System.out.println("Executing 'pwd' command");
        }
    };
    public abstract void execute();
}
public class EnumTest {
    public static void main(String[] args) {
        OSCommand.LS.execute();
        OSCommand.pwd.execute();
    }
}