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How to get an enum value from a string value in Java?


Question

Say I have an enum which is just

public enum Blah {
    A, B, C, D
}

and I would like to find the enum value of a string, for example "A" which would be Blah.A. How would it be possible to do this?

Is the Enum.valueOf() the method I need? If so, how would I use this?

2018/09/11
1
2022
9/11/2018 2:59:18 PM

Accepted Answer

Yes, Blah.valueOf("A") will give you Blah.A.

Note that the name must be an exact match, including case: Blah.valueOf("a") and Blah.valueOf("A ") both throw an IllegalArgumentException.

The static methods valueOf() and values() are created at compile time and do not appear in source code. They do appear in Javadoc, though; for example, Dialog.ModalityType shows both methods.

2017/09/09
2305
9/9/2017 10:26:47 PM

Another solution if the text is not the same to the enumeration value:

public enum Blah {
    A("text1"),
    B("text2"),
    C("text3"),
    D("text4");

    private String text;

    Blah(String text) {
        this.text = text;
    }

    public String getText() {
        return this.text;
    }

    public static Blah fromString(String text) {
        for (Blah b : Blah.values()) {
            if (b.text.equalsIgnoreCase(text)) {
                return b;
            }
        }
        return null;
    }
}
2019/02/08

Here's a nifty utility I use:

/**
 * A common method for all enums since they can't have another base class
 * @param <T> Enum type
 * @param c enum type. All enums must be all caps.
 * @param string case insensitive
 * @return corresponding enum, or null
 */
public static <T extends Enum<T>> T getEnumFromString(Class<T> c, String string) {
    if( c != null && string != null ) {
        try {
            return Enum.valueOf(c, string.trim().toUpperCase());
        } catch(IllegalArgumentException ex) {
        }
    }
    return null;
}

Then in my enum class I usually have this to save some typing:

public static MyEnum fromString(String name) {
    return getEnumFromString(MyEnum.class, name);
}

If your enums are not all caps, just change the Enum.valueOf line.

Too bad I can't use T.class for Enum.valueOf as T is erased.

2014/11/17

Use the pattern from Joshua Bloch, Effective Java:

(simplified for brevity)

enum MyEnum {
    ENUM_1("A"),
    ENUM_2("B");

    private String name;

    private static final Map<String,MyEnum> ENUM_MAP;

    MyEnum (String name) {
        this.name = name;
    }

    public String getName() {
        return this.name;
    }

    // Build an immutable map of String name to enum pairs.
    // Any Map impl can be used.

    static {
        Map<String,MyEnum> map = new ConcurrentHashMap<String, MyEnum>();
        for (MyEnum instance : MyEnum.values()) {
            map.put(instance.getName(),instance);
        }
        ENUM_MAP = Collections.unmodifiableMap(map);
    }

    public static MyEnum get (String name) {
        return ENUM_MAP.get(name);
    }
}

Also see:

Oracle Java Example using Enum and Map of instances

Execution order of of static blocks in an Enum type

How can I lookup a Java enum from its String value

2019/02/08

You should also be careful with your case. Let me explain: doing Blah.valueOf("A") works, but Blah.valueOf("a") will not work. Then again Blah.valueOf("a".toUpperCase(Locale.ENGLISH)) would work.

edit
Changed toUpperCase to toUpperCase(Locale.ENGLISH) based on tc. comment and the java docs

edit2 On android you should use Locale.US, as sulai points out.

2017/05/23

Here's a method that can do it for any Enum, and is case insensitive.

/** 
 * Finds the value of the given enumeration by name, case-insensitive. 
 * Throws an IllegalArgumentException if no match is found.  
 **/
public static <T extends Enum<T>> T valueOfIgnoreCase(
        Class<T> enumeration, String name) {

    for (T enumValue : enumeration.getEnumConstants()) {
        if (enumValue.name().equalsIgnoreCase(name)) {
            return enumValue;
        }
    }

    throw new IllegalArgumentException(String.format(
        "There is no value with name '%s' in Enum %s",
        name, enumeration.getName()
    ));
}
2015/04/22

Source: https://stackoverflow.com/questions/604424
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