java - 如何避免 java 中的重复枚举值？

Question

我有对应于编码的枚举。我需要检查枚举没有重复的编码数值。

public enum EncodingsEnum
{

ISO8859_1("ISO-8859-1",0), ISO8859_2("ISO-8859-2",1),
    ISO8859_3("ISO-8859-3",2), ISO8859_4("ISO-8859-4",3),
    ISO8859_5("ISO-8859-5",4), ISO8859_6("ISO-8859-6",5),
    ISO8859_7("ISO-8859-7",6), ISO8859_8("ISO-8859-8",7),
    ISO8859_9("ISO-8859-9",8), ISO8859_11("ISO-8859-11",9),
    ISO8859_13("ISO-8859-13",10),ISO8859_15("ISO-8859-15",11),
    UTF_8("UTF-8",11);

    public static final int ENCODINGS_COUNT = EncodingsEnum.values().length;
    private final String encodingName;
    private final int encodingNumber;

    EncodingsEnum(final String encodingName,int encodingNumber)
    {
        ReferenceChecker.checkReferenceNotNull(encodingName);

        this.encodingName = encodingName;
        this.encodingNumber = encodingNumber;
    }

    public static String getEncodingNameByNumber(int number)
    {
        for(EncodingsEnum encoding : EncodingsEnum.values())
        {
            if(encoding.encodingNumber == number)
            {
                return encoding.getEncodingName();
            }
        }
        throw new RuntimeException("Encoding with this number isn't supported:" + number);

    }

    public static int getEncodingNumberByName(final String name)
    {
        for(EncodingsEnum encoding : EncodingsEnum.values())
        {
            if(encoding.encodingName.equals(name))
            {
                return encoding.getEncodingNumber();
            }
        }
        throw new RuntimeException("Encoding with this name isn't supported:" + name);
    }

    public String getEncodingName()
    {
        return this.encodingName;
    }

    public int getEncodingNumber()
    {
        return this.encodingNumber;
    }
}

有一个问题，我可以创建与现有编码之一相同编号的编码，因此我需要检查枚举是否包含具有此编号的元素并抛出异常。但我不知道该怎么做。任何想法?谢谢。

Answer 1

这不应该在运行时检查:太晚了。添加一个循环访问枚举值的单元测试，并检查它们是否都有不同的数字。并确保始终执行单元测试，并检查它们是否通过，然后再生成新版本的应用程序/库。

@Test
public void encodingNumbersMustBeUnique() {
    Set<Integer> numbers = new HashSet<Integer>();
    for (EncodingsEnum e : EncodingsEnum.values()) {
        assertFalse(numbers.contains(e.getEncodingNumber()));
        numbers.add(e.getEncodingNumber());
    }
}