How to retrieve Enum name using the id?

Question

I have the enum as:

public enum EnumStatus {

    PASSED(40L, \"Has Passed\"),
    AVERAGE(60L, \"Has Average Marks\"),
    GOOD(80L, \"Has Good         


        

Answer 1

public static EnumStatus getById(long id)
{
  for (EnumStatus e : EnumStatus.values())
  {
    if (id == e.getId()) return e;
  } 
  throw new IllegalArgumentException("oh no");
}

Answer 2

This pattern can help you:

public interface Identifiable<T extends Number> {

    @Nonnull
    T getId();
}

public final class GettableById<K extends Number, V extends Enum<V> & Identifiable<K>> {

    @Nonnull
    private final Map<K, V> idToValue;


    public GettableById(@Nonnull V[] values) {
        this.idToValue = Arrays.stream(values)
                .collect(Collectors.toUnmodifiableMap(Identifiable::getId, v -> v));
    }

    @Nonnull
    public V getById(@Nonnull K id) {
        var value = idToValue.get(id);
        if (value != null) {
            return value;
        }
        throw new NullPointerException("Cannot get value by id: %s".formatted(id));
    }
}

public enum DataType implements Identifiable<Short> {

    ANNUAL((short) 1), QUARTERLY((short) 2);

    private static final GettableById<Short, DataType> companion = new GettableById<>(values());

    @Nonnull
    private final Short id;


    public static DataType getById(Short id) {
        return companion.getById(id);
    }

    DataType(@Nonnull Short id) {
        this.id = id;
    }

    @Nonnull
    @Override
    public Short getId() {
        return id;
    }
}

Answer 3

Create a static method in your enum which searches in values (implicit method/member, don't know exactly which is it) and returns the corresponding value. For cases in which the method can not find a matching value, you should create a special entry, e.g. UNKNOWN, which you can return. This way, you do not have to return null, which is always a bad idea.

public static EnumStatus getById(Long id) {
    for(EnumStatus e : values()) {
        if(e.id.equals(id)) return e;
    }
    return UNKNOWN;
}

Btw - your code seems to be wrong. The bracket after GOOD seems to not belong there.

Answer 4

You make this work as follows:

public static String fromId(long id) {
        for (EnumStatus es : EnumStatus.values()) {
            if (es.id.equals(id)) {
                return es.getName();
            }
        }
        throw new IllegalArgumentException();
}

Answer 5

Iterate over all the values and compare Id

for (EnumStatus  enumStatus : EnumStatus.values()) {
   if (..) {..}
}