Java 中带有自定义值的枚举

原文:https://www.geeksforgeeks.org/enum-customized-value-java/

先决条件:Java 中的枚举

默认情况下，枚举有自己的字符串值，我们也可以给枚举分配一些自定义值。考虑下面的例子。

示例:

enum  Fruits
{
    APPLE(“RED”), BANANA(“YELLOW”), GRAPES(“GREEN”);
}

在上面的例子中，我们可以看到水果枚举有三个成员，即苹果、香蕉和葡萄，它们分别有自己不同的自定义值红色、黄色和绿色。

现在要在代码中使用这个枚举，我们必须遵循以下几点:-

  1. We must create a parameterized constructor for this enumeration class. Why? Because we know that enumeration class objects cannot be explicitly created, we use parameterized constructors when initializing. The constructor cannot be public or protected, it must have a private or default modifier. Why? If we create public or protected, it will allow multiple objects to be initialized. This completely violates the concept of enumeration.
  2. We must create a getter method to get the value of the enumeration.
// Java program to demonstrate how values can
// be assigned to enums.
enum TrafficSignal
{
    // This will call enum constructor with one
    // String argument
    RED("STOP"), GREEN("GO"), ORANGE("SLOW DOWN");

    // declaring private variable for getting values
    private String action;

    // getter method
    public String getAction()
    {
        return this.action;
    }

    // enum constructor - cannot be public or protected
    private TrafficSignal(String action)
    {
        this.action = action;
    }
}

// Driver code
public class EnumConstructorExample
{
    public static void main(String args[])
    {
        // let's print name of each enum and there action
        // - Enum values() examples
        TrafficSignal[] signals = TrafficSignal.values();

        for (TrafficSignal signal : signals)
        {
            // use getter method to get the value
            System.out.println("name : " + signal.name() +
                        " action: " + signal.getAction() );
        }
    }
}

输出:

name : RED action: STOP
name : GREEN action: GO 
name : ORANGE action: SLOW DOWN

本文由 维杭沙阿 供稿。如果你喜欢 GeeksforGeeks 并想投稿，你也可以使用contribute.geeksforgeeks.org写一篇文章或者把你的文章邮寄到 contribute@geeksforgeeks.org。看到你的文章出现在极客博客主页上，帮助其他极客。

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