Get enum values as List of String in Java 8

Question

Is there any Java 8 method or easy way, which returns Enum values as a List of String, like:

List<String> sEnum = getEnumValuesAsString(); 

Answer 1

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()); 

Answer 2

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