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

This can be done using a static map along with a static initializer:

public enum EnumStatus {

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

    private static final Map byId = new HashMap();
    static {
        for (EnumStatus e : EnumStatus.values()) {
            if (byId.put(e.getId(), e) != null) {
                throw new IllegalArgumentException("duplicate id: " + e.getId());
            }
        }
    }

    public static EnumStatus getById(Long id) {
        return byId.get(id);
    }

    // original code follows

    private java.lang.String name;

    private java.lang.Long id;

    EnumStatus(Long id, java.lang.String name) {
        this.name = name;
        this.id = id;
    }

    public java.lang.String getName() {
        return name;
    }

    public java.lang.Long getId() {
        return id;
    }

}

This will give an O(1) getById() method, and will automatically detect if you accidentally have duplicate ids in the enum.