How to Use Enum valueOf Method in Java

In Java, use EnumType.valueOf(String name) to convert a string to its matching enum constant. The string must exactly match the enum constant's name, or it throws an IllegalArgumentException. This method helps convert text input into enum values.

Syntax

The valueOf method is a static method of an enum type that takes a String argument representing the name of the enum constant.

• EnumType.valueOf(String name): Returns the enum constant of the specified enum type with the specified name.
• The name must match exactly an identifier used to declare an enum constant in this type.

java

EnumType.valueOf(String name)

Example

This example shows how to convert a string to an enum constant using valueOf. It prints the enum constant and its ordinal position.

java

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

    public static void main(String[] args) {
        String input = "WEDNESDAY";
        Day day = Day.valueOf(input);
        System.out.println("Enum constant: " + day);
        System.out.println("Ordinal position: " + day.ordinal());
    }
}

Output

Enum constant: WEDNESDAY
Ordinal position: 2

Common Pitfalls

Common mistakes when using valueOf include:

• Passing a string that does not exactly match any enum constant name causes IllegalArgumentException.
• Enum names are case-sensitive, so "monday" will fail if the enum constant is "MONDAY".
• Passing null throws NullPointerException.

To avoid errors, validate input or use try-catch to handle exceptions.

java

public class EnumValueOfPitfall {
    enum Color {
        RED, GREEN, BLUE
    }

    public static void main(String[] args) {
        try {
            String input = "green"; // lowercase, will cause exception
            Color color = Color.valueOf(input);
        } catch (IllegalArgumentException e) {
            System.out.println("Invalid enum constant: " + e.getMessage());
        }
    }
}

Output

Invalid enum constant: No enum constant EnumValueOfPitfall.Color.green

Quick Reference

• Method: EnumType.valueOf(String name)
• Input: Exact name of enum constant (case-sensitive)
• Returns: Enum constant matching the name
• Throws: IllegalArgumentException if no match, NullPointerException if null
• Use case: Convert string input to enum safely

Key Takeaways

Use EnumType.valueOf(String) to convert a string to an enum constant.

The string must exactly match the enum constant name, including case.

Handle IllegalArgumentException to catch invalid inputs safely.

Passing null to valueOf causes NullPointerException.

Use valueOf to map text input to enum values in your programs.