在 Java8中以字符串列表的形式获取枚举值

有没有任何 Java8方法或简单的方法，可以将 Enum 值作为 String 列表返回，比如:

List<String> sEnum = getEnumValuesAsString();
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最佳答案

You can do (pre-Java 8):

List<Enum> enumValues = Arrays.asList(Enum.values());

or 

List<Enum> enumValues = new ArrayList<Enum>(EnumSet.allOf(Enum.class));

Using Java 8 features, you can map each constant to its name:

List<String> enumNames = Stream.of(Enum.values())
.map(Enum::name)
.collect(Collectors.toList());
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You could also do something as follow

public enum DAY {MON, TUES, WED, THU, FRI, SAT, SUN};
EnumSet.allOf(DAY.class).stream().map(e -> e.name()).collect(Collectors.toList())

or 

EnumSet.allOf(DAY.class).stream().map(DAY::name).collect(Collectors.toList())

The main reason why I stumbled across this question is that I wanted to write a generic validator that validates whether a given string enum name is valid for a given enum type (Sharing in case anyone finds useful).

For the validation, I had to use Apache's EnumUtils library since the type of enum is not known at compile time. 

@SuppressWarnings({ "unchecked", "rawtypes" })
public static void isValidEnumsValid(Class clazz, Set<String> enumNames) {
Set<String> notAllowedNames = enumNames.stream()
.filter(enumName -> !EnumUtils.isValidEnum(clazz, enumName))
.collect(Collectors.toSet());


if (notAllowedNames.size() > 0) {
String validEnumNames = (String) EnumUtils.getEnumMap(clazz).keySet().stream()
.collect(Collectors.joining(", "));


throw new IllegalArgumentException("The requested values '" + notAllowedNames.stream()
.collect(Collectors.joining(",")) + "' are not valid. Please select one more (case-sensitive) "
+ "of the following : " + validEnumNames);
}
}

I was too lazy to write an enum annotation validator as shown in here https://stackoverflow.com/a/51109419/1225551

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If you need to go to an array, you can do this:

public enum DAY {MON, TUES, WED, THU, FRI, SAT, SUN};


String[] days = Stream.of(DAY.values()).map(Enum::name).toArray(String[]::new);

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