How to fetch a subset of an enumeration

Question

Most of the times an enumeration containing all elements is shown in a drop down in the user interface. We have a need to show only 2 out of 5 fields in the user interface. What would be an easier way to fetch this data, by somehow leveraging the same functions available for an enumeration.

enum Color {RED, GREEN, BLACK, BLUE, YELLOW};

We have a requirement to show only {RED, BLUE} in a certain user interface?

Answer 1

Sounds like a job for EnumSet:

EnumSet<Color> set = EnumSet.of(Color.RED, Color.BLUE);

Answer 2

EnumSet.of(Color.RED, Color.BLUE)

see java.util.EnumSet

Answer 3

If enum contains some custom methods (e.g., to display Red instesd of RED)

public enum Color {
    RED("Red"), GREEN("Green"), BLACK("Black"), BLUE("Blue"), YELLOW("Yellow");

    private final String display;

    private Color(String display) {
        this.display = display;
    }

    @Override
    public String toString() {
        return display;
    }

    public static EnumSet<Color> getSubSetOfValues() {
        return EnumSet.of(RED, BLUE); // return Red and Green
        //return EnumSet.range(GREEN, BLUE); // return Green, Black and Blue
    }
}

Color.values(); // all elements.

Color.getSubSetOfValues(); // subset