How to Retrieve Java Enum Types from Their String Values

How do I find a Java Enum type given a string value?

public enum Day {
    MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY;
}

In Java, enumerations (enums) are special data types that allow a variable to be a set of predefined constants. Retrieving an Enum type from a string value requires matching the string with Enum constants. This guide will show you how to do this effectively using built-in methods.

try {
    Day day = Day.valueOf("MONDAY"); // Successfully retrieves MONDAY Enum.
} catch (IllegalArgumentException e) {
    System.out.println("No matching Enum for the value.");
}

Causes

• The string value might not match any Enum constant due to case sensitivity.
• The string may contain extra whitespace or different formatting than Enum constant names.

Solutions

• Use the `valueOf()` method of the Enum class, which can convert a string to an Enum constant if the string matches exactly.
• Handle potential exceptions by using a try-catch block when converting to avoid runtime errors.
• Implement a custom method to handle case-insensitive matching if necessary.

Mistake: Attempting to retrieve an Enum with incorrect casing (e.g., "monday").

Solution: Always match the string exactly with the Enum name, or use `toUpperCase()` or `toLowerCase()` for comparisons.

Mistake: Forgetting to catch `IllegalArgumentException` when using `valueOf()`.

Solution: Wrap the `valueOf()` call in a try-catch block to handle potential exceptions.