How can I get Enum fields names using reflection in Java?

Question

This is my class:

public enum Currency {
    NIS, USD, EUR, GBP, JPY, AUD, CAD, DKK, NOK, ZAR, SEK, CHF, JOD, LBP, EGP;

    private String name;
    private int unit;
    private String country;
    private double rate;
    private double change;
}

When I tried to get the fields names of this class using reflection I got the private fields and the enum constants (NIS,EUR,....)

How can I get only the private fields names?

Answer 1

UPDATE

From your comment, try the following. It also does not pick up any public fields if you were to have any.

    Field[] allFields = Currency.class.getDeclaredFields();
    for (Field field : allFields) {
        if (Modifier.isPrivate(field.getModifiers())) {
            System.out.println(field.getName());
        }
    }

Results:

To get rid of the $VALUES from the result check if the field is not synthetic

    Field[] allFields = Currency.class.getDeclaredFields();
    for (Field field : allFields) {
        if (Modifier.isPrivate(field.getModifiers()) && !field.isSynthetic()) {
            System.out.println(field.getName());
        }
    }

Results:

As far as giving values to these fields and accessing them you don't need to do reflection to do this. You just need to define the fields appropriately with each enum as followed.

public enum Currency {
    NIS("Name1", 0, "NIS", 1, 2), 
    USD("Name2", 1, "USD", 1, 2), 
    EUR("Name3", 2, "EUR", 1, 2), 
    GBP("Name4", 3, "GBP", 1, 2), 
    JPY("Name5", 4, "JPY", 1, 2), 
    AUD("Name6", 5, "AUD", 1, 2), 
    CAD("Name7", 6, "CAD", 1, 2), 
    DKK("Name8", 7, "DKK", 1, 2), 
    NOK("Name9", 8, "NOK", 1, 2), 
    ZAR("Name10", 9, "ZAR", 1, 2), 
    SEK("Name11", 10, "SEK", 1, 2), 
    CHF("Name12", 11, "CHF", 1, 2), 
    JOD("Name13", 12, "JOD", 1, 2), 
    LBP("Name14", 13, "LBP", 1, 2), 
    EGP("Name15", 14, "EGP", 1, 2);

    private final String name;
    private final int unit;
    private final String country;
    private final double rate;
    private final double change;

    private Currency(String name, int unit, String country, double rate, double change) {
        this.name = name;
        this.unit = unit;
        this.country = country;
        this.rate = rate;
        this.change = change;
    }

    public String getName() {
        return name;
    }

    public int getUnit() {
        return unit;
    }

    public String getCountry() {
        return country;
    }

    public double getRate() {
        return rate;
    }

    public double getChange() {
        return change;
    }
}

The usage of this would be:

public static void main(String[] args) throws Exception {
    for (Currency currency : Currency.values()) {
        System.out.println("Name: " + currency.getName());
        System.out.println("Unit: " + currency.getUnit());
        System.out.println("Country: " + currency.getCountry());
        System.out.println("Rate: " + currency.getRate());
        System.out.println("Change: " + currency.getChange());
        System.out.println("");
    }
}

Results (Not all results are displayed):

Or you can directly use an enum as followed:

System.out.println(Currency.AUD.getName() + " " + Currency.AUD.getCountry());

Result:

Name6 AUD

Answer 2

Try test Field.isEnumConstant()

Also you can check getModifiers() and test if it's static, private, etc.

Also isSynthetic() might be needed for testing too.

Answer 3

This code should do it (based on bayou.io's answer):

List<String> fields = Arrays.stream(Currency.class.getDeclaredFields())
        .filter(x -> !x.isEnumConstant() && !x.isSynthetic())
        .map(x -> x.getName())
        .collect(Collectors.toList());

It just iterates all the fields, filtering the ones that aren't enum constants nor synthetic (like the $VALUES field).