枚举就像类。与类一样，它也有方法和属性。

不同阶级的区别是: 1. 枚举常量是public, static, final。 2. 枚举不能用于创建对象，也不能扩展其他类。但是它可以实现接口。

Enum表示枚举，即逐个提到(一些事情)。

enum是一种包含固定常数集的数据类型。

OR

枚举就像一个类，在编译时有一组固定的实例。

例如:

public class EnumExample {
    interface SeasonInt {
        String seasonDuration();
    }

    private enum Season implements SeasonInt {
        // except the enum constants remaining code looks same as class
        // enum constants are implicitly public static final we have used all caps to specify them like Constants in Java
        WINTER(88, "DEC - FEB"), SPRING(92, "MAR - JUN"), SUMMER(91, "JUN - AUG"), FALL(90, "SEP - NOV");

        private int days;
        private String months;

        Season(int days, String months) { // note: constructor is by default private 
            this.days = days;
            this.months = months;
        }

        @Override
        public String seasonDuration() {
            return this+" -> "+this.days + "days,   " + this.months+" months";
        }

    }
    public static void main(String[] args) {
        System.out.println(Season.SPRING.seasonDuration());
        for (Season season : Season.values()){
            System.out.println(season.seasonDuration());
        }

    }
}

枚举的优点:

Enum提高了编译时检查的类型安全性，以避免在运行时出现错误。 枚举可以很容易地用于交换机 枚举可以遍历 枚举可以有字段、构造函数和方法 enum可以实现许多接口，但不能扩展任何类，因为它在内部扩展了enum类

更多的

除了@BradB，回答:

That is so true... It's strange that it is the only answer who mention that. When beginners discover enums, they quickly take that as a magic-trick for valid identifier checking for the compiler. And when the code is intended to be use on distributed systems, they cry... some month later. Maintain backward compatibility with enums that contains non static list of values is a real concern, and pain. This is because when you add a value to an existing enum, its type change (despite the name does not).

"Ho, wait, it may look like the same type, right? After all, they’re enums with the same name – and aren’t enums just integers under the hood?" And for these reasons, your compiler will likely not flag the use of one definition of the type itself where it was expecting the other. But in fact, they are (in most important ways) different types. Most importantly, they have different data domains – values that are acceptable given the type. By adding a value, we’ve effectively changed the type of the enum and therefore break backward compatibility.

总之:当你想使用它的时候使用它，但是，请检查所使用的数据域是一个有限的、已知的、固定的集合。

Enum继承Object类和抽象类Enum的所有方法。所以你可以使用它的方法来反射、多线程、序列化、可比性等等。如果你只是声明一个静态常量而不是Enum，你就不能。除此之外，Enum的值也可以传递给DAO层。

下面是要演示的示例程序。

public enum State {

    Start("1"),
    Wait("1"),
    Notify("2"),
    NotifyAll("3"),
    Run("4"),
    SystemInatilize("5"),
    VendorInatilize("6"),
    test,
    FrameworkInatilize("7");

    public static State getState(String value) {
        return State.Wait;
    }

    private String value;
    State test;

    private State(String value) {
        this.value = value;
    }

    private State() {
    }

    public String getValue() {
        return value;
    }

    public void setCurrentState(State currentState) {
        test = currentState;
    }

    public boolean isNotify() {
        return this.equals(Notify);
    }
}

public class EnumTest {

    State test;

    public void setCurrentState(State currentState) {
        test = currentState;
    }

    public State getCurrentState() {
        return test;
    }

    public static void main(String[] args) {
        System.out.println(State.test);
        System.out.println(State.FrameworkInatilize);
        EnumTest test=new EnumTest();
        test.setCurrentState(State.Notify);
        test. stateSwitch();
    }

    public void stateSwitch() {
        switch (getCurrentState()) {
        case Notify:
            System.out.println("Notify");
            System.out.println(test.isNotify());
            break;
        default:
            break;
        }
    }
}

枚举?为什么要使用它?我认为当你使用它的时候会更容易理解。我也有同样的经历。

假设您有一个创建、删除、编辑和读取数据库操作。

现在如果你创建一个枚举作为一个操作:

public enum operation {
    create("1")
    delete("2")
    edit("3")
    read("4")

    // You may have is methods here
    public boolean isCreate() {
        return this.equals(create);
    }
    // More methods like the above can be written

}

现在，你可以这样声明:

private operation currentOperation;

// And assign the value for it 
currentOperation = operation.create

所以你可以在很多方面使用它。对于特定的事情使用enum总是好的，因为上面例子中的数据库操作可以通过检查currentOperation来控制。也许有人会说，这也可以用变量和整数值来实现。但我相信Enum更安全，更适合程序员。

另一件事:我认为每个程序员都喜欢布尔，不是吗?因为它只能存储两个值，两个特定的值。所以Enum可以被认为具有相同类型的功能，用户可以定义它将存储多少和什么类型的值，只是方式略有不同。：）

让我恍然大悟的是:Enum有一个私有构造函数，只能通过公共枚举来访问:

enum RGB {
    RED("Red"), GREEN("Green"), BLUE("Blue");

    public static final String PREFIX = "color ";

    public String getRGBString() {
        return PREFIX + color;
    }

    String color;

    RGB(String color) {
        this.color = color;
    }
}

public class HelloWorld {
    public static void main(String[] args) {
        String c = RGB.RED.getRGBString();
        System.out.print("Hello " + c);
    }
}