How to set value for one enum?

Question

I have the following enum:

enum ColumnType {
    TEXT,
    NUMERIC,
    DATE
}

When using this enum, I need to be able to specify a date format String if using the DATE value. How would I do that?

For instance, in my code I want to call a method using something similar to this:

foo(ColumnType.DATE("yyyyMMdd");

Later I would need to be able to retrieve that value using object.getColumnType.getDateFormat() if the ColumnType is DATE. Is this even possible?

The documentation I've been able to find so far suggest ways to set the value of an enum but they all show how to set it for all the enum values, not an individual one.

My understanding of enums is fairly basic so I apologize if this isn't worded correctly. Thanks!

EDIT:

The date format needs to be set at runtime as the user will be selecting/entering the date format string.

Answer 1

You can implement two constructors and pass the Date format mask if necessary, but it can't be changed at runtime:

public enum ColumnType {
    TEXT,
    NUMERIC,
    DATE("yyyyMMdd");

    private final String dateMask;

    public String getDateMask() {
        return dateMask;
    }

    ColumnType(String dateMask) {
        this.dateMask = dateMask;
    }

    ColumnType() {
        this.dateMask = null;
    }
}

public class Main {
    public static void main(String[] args) {
        System.out.println(ColumnType.DATE.getDateMask());

    }
}

Answer 2

You can do

enum ColumnType {
    TEXT,
    NUMERIC,
    DATE_YYYYMMDD,
    oher date format
}

However, if you want arbitrary formats you need a class to wrap these

class ColumnTypeFormat {
    ColumnType columnType;
    String format;
}

foo(new ColumnTypeFormat(ColumnType.DATE, "yyyyMMdd"));

You can combine these with a common interface

interface ColumnType {
    String getFormat();
    Class getType();
}

enum SimpleColumnType implements ColumnType {
    TEXT(String.class, "%s"),
    NUMERIC(BigDecimal .class, "%f");

    private Class type;
    private String format;

    SimpleColumnType(Class type, String format) {
        this.type = type;
        this.format = format;
    }

    @Override
    public Class getType() { return type; }

    @Override
    public String getFormat() { return format; }
}

class DateColumnType implements ColumnType {
    private final String format;

    public DateColumnType(String format) {
        this.format = format;
    }

    @Override
    public Class getType() { return LocalDate.class; }

    @Override
    public String getFormat() { return format; }
}

This allows you to have some fixed, pre-created types in the enum but also create additional ones on the fly with a common interface.

Answer 3

Now as OP only wants to pass the dateFormat dynamically, hence following code suits better,

public static void main(String[] args) {
    ColumnTypeValue columnTypeNumeric = new ColumnTypeValue(ColumnType.NUMERIC);
    ColumnTypeValue columnTypeText = new ColumnTypeValue(ColumnType.TEXT);
    ColumnTypeValue columnTypeDate = new ColumnTypeValue("yyyyMMdd");
}

public static class ColumnTypeValue {
    ColumnType columnType;
    String dateFormat;

    public ColumnTypeValue(ColumnType columnType) {
        this.columnType = columnType;
    }

    public ColumnTypeValue(String dateFormat) {
        this.columnType = ColumnType.DATE;
        this.dateFormat = dateFormat;
    }
}

enum ColumnType {
    TEXT, NUMERIC, DATE;
}