Question
How can I check if a specific string exists within a Java enum?
enum Choices { a1, a2, b1, b2 };
Answer
In Java, enums do not directly support a method like `ArrayList.contains()` for checking if they contain a specific value in the form of a string. However, you can achieve this functionality by creating a method to check each enum constant's name or by leveraging the built-in `valueOf()` method of enums to determine if a string corresponds to any of the defined enum constants.
public enum Choices { a1, a2, b1, b2;
public static boolean contains(String str) {
for (Choices choice : Choices.values()) {
if (choice.name().equalsIgnoreCase(str)) {
return true;
}
}
return false;
}
}
// Usage:
if (Choices.contains("a1")) {
// execute this block
}
Causes
- Enums do not have a built-in method for string comparison like lists do.
- Enums are strong types; they represent a fixed set of constants, unlike dynamic collections.
Solutions
- Define a helper method within the enum that checks for the presence of a value based on string comparison.
- Use the `valueOf()` method to attempt retrieving an enum constant and handle exceptions to determine if it exists.
Common Mistakes
Mistake: Forgetting to handle case sensitivity when matching strings to enum names.
Solution: Use `equalsIgnoreCase()` instead of `equals()` to ensure that the check is case insensitive.
Mistake: Assuming the enum's constants can be directly compared to arbitrary strings without a helper method.
Solution: Implement a method within the enum to encapsulate the logic for checking string presence.
Helpers
- Java enum check string
- Java enum contains string
- Java enum methods
- Java enum valueOf
- Java enum string comparison
