Question

我想做这样的事情：

public class MyEnumTest {

    public enum MyEnum;
    private MyEnum value;

    public MyEnumTest(enum e)
    {
        this.MyEnum = e; 
        this.value = this.MyEnum.values[0]//Set value to the first enum value.
    }

    public void setValue(MyEnum e)
    {
        this.value = e; 
    }

    public MyEnum getValue()
    {
        return value;
    }

}

并称之为：

MyEnumTest car = new MyEnumTest({HONDA, FORD, TOYOTA, HOLDEN}); 
MyEnumTest fruit = new MyEnumTest({APPLE, BANANA, CHERRY}); 

/* some operations occur*/ 

if (car.getValue() == car.FORD) System.out.println("Vrooom!"); 
if (fruit.getValue()) == fruit.APPLE) System.out.println ("Is red and round and delicious");

这样做有什么想法吗？

对于奖励标记 - 是否可以使用枚举值设置初始值？例如

之类的东西

MyEnumTest myET = new myEnumTest(new enum {RED, GREEN, BLUE, YELLOW}, BLUE);

Answer 1

您可以使用（不使用enum关键字）：

public MyEnumTest(MyEnum e)
{
    this.myEnum = e; 
    this.value = MyEnum.values()[0];
}

对于第2部分，您可以定义重载的构造函数：

public MyEnumTest(MyEnum[] myEnums) {

并使用：

MyEnumTest myET = new MyEnumTest(new MyEnum[] { MyEnum.FOO, ... });

Answer 2

正如其他人所说，很难理解你想要做什么，但这是我最好的猜测：

public enum Color {
    RED, GREEN, YELLOW, BLUE;
}


public class MyEnumTest<E extends Enum<E>> {
    private final Class<E> enumType;
    private final E value; 

    public Class<E> getEnumType() {
        return enumType;
    }

    public E getValue() {
        return value;
    }

    public MyEnumTest(Class<E> enumType, E value) {
        this.enumType = enumType;
        this.value = value;
    }

    public MyEnumTest(Class<E> enumType) {
        this(enumType, enumType.getEnumConstants()[0]);
    }

    public static void main(String... args) {
        // no initial value provided
        MyEnumTest<Color> myET = new MyEnumTest<Color>(Color.class);
        if (myET.getValue() == Color.RED) {
            System.out.println("It's probably an apple");
        }

        // providing an initial value
        myET = new MyEnumTest<Color>(Color.class, Color.YELLOW);
        if (myET.getValue() == Color.YELLOW) {
            System.out.println("It's probably a banana");
        }
    }
}

另外，请记住，枚举值是静态的...所以，像myET.MyEnum.RED这样的东西没有意义......你应该使用：Color.RED

Answer 3

很难说出你想要做什么。 Reimeus的答案显示了如何处理您的特定MyEnum作为参数。如果要将类实现为使用任何枚举，请使用以下命令：

public class MyEnumTest<E extends Enum<E>> {

    private final E firstValue;

    public MyEnumTest(Class<E> enumType)
    {
        this.firstValue = enumType.getEnumConstants()[0];
    }

    ...
}

并像这样实例化：

MyEnumTest myET = new myEnumTest(MyEnum.class);

如何将枚举传递给构造函数？

3 个答案: