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

User · Answer

Kotlin Solution

Create an extension and then call valueOf<MyEnum>("value"). If the type is invalid, you'll get null and have to handle it

inline fun <reified T : Enum<T>> valueOf(type: String): T? {
    return try {
        java.lang.Enum.valueOf(T::class.java, type)
    } catch (e: Exception) {
        null
    }
}

Alternatively, you can set a default value, calling valueOf<MyEnum>("value", MyEnum.FALLBACK), and avoiding a null response. You can extend your specific enum to have the default be automatic

inline fun <reified T : Enum<T>> valueOf(type: String, default: T): T {
    return try {
        java.lang.Enum.valueOf(T::class.java, type)
    } catch (e: Exception) {
        default
    }
}

Or if you want both, make the second:

inline fun <reified T : Enum<T>> valueOf(type: String, default: T): T = valueOf<T>(type) ?: default

User · Answer

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

User · Answer

java lang Enum defines several useful methods  which is available to all enumeration type in Java    You can use name   method to get name of any Enum constants  String literal used to write enum constants is their name  Similarly values   method can be used to get an array of all Enum constants from an Enum type  And for the asked question  you can use valueOf   method to convert any String to Enum constant in Java  as shown below      public class EnumDemo06       public static void main String args              Gender fromString   Gender valueOf  MALE            System out println  Gender MALE name         fromString name                private enum Gender           MALE  FEMALE           Output  Gender MALE name     MALE   In this code snippet  valueOf   method returns an Enum constant Gender MALE  calling name on that returns  MALE

User · Answer

Using Blah valueOf string  is best but you can use Enum valueOf Blah class  string  as well

User · Answer

Solution using Guava libraries  Method getPlanet    is case insensitive  so getPlanet   MerCUrY   will return Planet MERCURY   package com universe solarsystem planets  import org apache commons lang3 StringUtils  import com google common base Enums  import com google common base Optional     Pluto and Eris are dwarf planets  who cares  public enum Planet      MERCURY     VENUS     EARTH     MARS     JUPITER     SATURN     URANUS     NEPTUNE      public static Planet getPlanet String name          String val   StringUtils trimToEmpty name  toUpperCase          Optional  lt Planet gt  possible   Enums getIfPresent Planet class  val         if   possible isPresent               throw new IllegalArgumentException val      There is no such planet                   return possible get

User · Answer

In Java 8 the static Map pattern is even easier and is my preffered method  If you want to use the Enum with Jackson you can override toString and use that instead of name  then annotate with  JsonValue  public enum MyEnum       BAR      BAZ      private static final Map lt String  MyEnum gt  MAP   Stream of MyEnum values    collect Collectors toMap Enum  name  Function identity          public static MyEnum fromName String name           return MAP get name            public enum MyEnumForJson       BAR  bar        BAZ  baz        private static final Map lt String  MyEnumForJson gt  MAP   Stream of MyEnumForJson values    collect Collectors toMap Object  toString  Function identity          private final String value       MyEnumForJson String value            this value   value              JsonValue      Override     public String toString             return value             public static MyEnumForJson fromValue String value           return MAP get value

User · Answer

My 2 cents here  using Java8 Streams   checking an exact string   public enum MyEnum       VALUE 1  Super        VALUE 2  Rainbow        VALUE 3  Dash        VALUE 3  Rocks         private final String value       MyEnum String value            this value   value                         return the Enum representation for the given string          throws IllegalArgumentException if unknown string              public static MyEnum fromString String s  throws IllegalArgumentException           return Arrays stream MyEnum values                     filter v - gt  v value equals s                    findFirst                    orElseThrow    - gt  new IllegalArgumentException  unknown value      s                 EDIT     Renamed the function to fromString   since naming it using that convention  you ll obtain some benefits from Java language itself  for example    Direct conversion of types at HeaderParam annotation

User · Answer

Fastest way to get the name of enum is to create a map of enum text and value when the application start  and to get the name call the function Blah getEnumName     public enum Blah       A  text1        B  text2        C  text3        D  text4         private String text      private HashMap lt String  String gt  map      Blah String text        this text   text             public String getText           return this text             static        createMapOfTextAndName               public static void createMapOfTextAndName             map   new HashMap lt String  String gt             for  Blah b   Blah values                   map put b getText   b name                         public static String getEnumName String text            return map get text toLowerCase

User · Answer

Use the pattern from Joshua Bloch  Effective Java   simplified for brevity  enum MyEnum       ENUM 1  quot A quot        ENUM 2  quot B quot         private String name       private static final Map lt String MyEnum gt  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 lt String MyEnum gt  map   new ConcurrentHashMap lt String  MyEnum gt             for  MyEnum instance   MyEnum values                  map put instance getName   toLowerCase   instance                     ENUM MAP   Collections unmodifiableMap map              public static MyEnum get  String name            return ENUM MAP get name toLowerCase              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

User · Answer

Apache s commons-lang library has a static function org apache commons lang3 EnumUtils getEnum which will map a String to your Enum type  Same answer essentially as Geoffreys but why roll your own when it s out there in the wild already

User · Answer

In Java 8 or later  using Streams   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 Optional lt Blah gt  fromText String text            return Arrays stream values               filter bl - gt  bl text equalsIgnoreCase text              findFirst

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O 1  method inspired from thrift generated code which utilize a hashmap   public enum USER           STUDENT  jon  0  TEACHER  tom  1            private static final Map lt String  Integer gt  map   new HashMap lt  gt              static                   for  USER user   EnumSet allOf USER class                             map put user getTypeName    user getIndex                                          public static int findIndexByTypeName String typeName                    return map get typeName                      private USER String typeName int index                   this typeName   typeName                  this index   index                    private String typeName          private int index          public String getTypeName                     return typeName                    public void setTypeName String typeName                    this typeName   typeName                    public int getIndex                     return index                    public void setIndex int index                    this index   index

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Another way of doing this by using implicit static method name   of Enum  name will return the exact string used to create that enum which can be used to check against provided string   public enum Blah        A  B  C  D       public static Blah getEnum String s           if A name   equals s                return A           else if B name   equals s                return B           else if C name   equals s                return C           else if  D name   equals s                return D                    throw new IllegalArgumentException  No Enum specified for this string              Testing   System out println Blah getEnum  B   name         it will print B  B   inspiration  10 Examples of Enum in Java

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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  lt T extends Enum lt T gt  gt  T valueOfIgnoreCase          Class lt T gt  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

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As a switch-version has not been mentioned yet I introduce it  reusing OP s enum      private enum Blah       A  B  C  D       public static Blah byName String name          switch  name            case  A             return A          case  B             return B          case  C             return C          case  D             return D          default            throw new IllegalArgumentException               No enum constant     Blah class getCanonicalName           name                       Since this don t give any additional value to the valueOf String name  method  it only makes sense to define an additional method if we want have a different behavior  If we don t want to raise an IllegalArgumentException we can change the implementation to     private enum Blah       A  B  C  D       public static Blah valueOfOrDefault String name  Blah defaultValue          switch  name            case  A             return A          case  B             return B          case  C             return C          case  D             return D          default            if  defaultValue    null                throw new NullPointerException                          return defaultValue                      By providing a default value we keep the contract of Enum valueOf String name  without throwing an IllegalArgumentException  in that manner that in no case null is returned  Therefore we throw a NullPointerException if the name is null and in case of default if defaultValue is null  That s how valueOfOrDefault works   This approach adopts the design of the Map-Interface which provides a method Map getOrDefault Object key  V defaultValue  as of Java 8

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I like to use this sort of process to parse commands as strings into enumerations   I normally have one of the enumerations as  unknown  so it helps to have that returned when the others are not found  even on a case insensitive basis  rather than null  that meaning there is no value    Hence I use this approach   static  lt E extends Enum lt E gt  gt  Enum getEnumValue String what  Class lt E gt  enumClass        Enum lt E gt  unknown null      for  Enum lt E gt  enumVal  enumClass getEnumConstants                if  what compareToIgnoreCase enumVal name       0                return enumVal                    if  enumVal name   compareToIgnoreCase  unknown      0                unknown enumVal                        return unknown

User · Answer

What about   public enum MyEnum       FIRST      SECOND      THIRD       public static Optional lt MyEnum gt  fromString String value           try              return Optional of MyEnum valueOf value             catch Exception e               return Optional empty

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public static MyEnum getFromValue String value        MyEnum resp   null      MyEnum nodes     values        for int i   0  i  lt  nodes length  i              if nodes i  value equals value                 resp   nodes i               break                      return resp

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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

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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

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You may need to this    public enum ObjectType       PERSON  Person         public String parameterName       ObjectType String parameterName            this parameterName   parameterName             public String getParameterName             return this parameterName               From String method will return you the Enum for the provided input string     public static ObjectType fromString String parameterName            if  parameterName    null                for  ObjectType objType   ObjectType values                      if  parameterName equalsIgnoreCase objType parameterName                         return objType                                                    return null            One More Addition       public static String fromEnumName String parameterName            if  parameterName    null                for  DQJ objType   DQJ values                      if  parameterName equalsIgnoreCase objType name                           return objType parameterName                                                    return null          This will return you the Value by a Stringified Enum Name For e g  if you provide  PERSON  in the fromEnumName it ll return you the Value of Enum i e   Person

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To add to the previous answers  and address some of the discussions around nulls and NPE I m using Guava Optionals to handle absent invalid cases   This works great for URI parameter parsing   public enum E       A B C      public static Optional lt E gt  fromString String s            try               return Optional of E valueOf s toUpperCase                catch  IllegalArgumentException NullPointerException e                return Optional absent                        For those not aware  here s some more info on avoiding null with Optional  https   code google com p guava-libraries wiki UsingAndAvoidingNullExplained Optional

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I was looking for an answer to find the  quot blah quot  name and not its value  not the text   base on  Manu   Mano answer I find this code useful  public enum Blah   A  quot text1 quot    B  quot text2 quot    C  quot text3 quot    D  quot text4 quot     private String text   Blah String text    this text   text     public String getText       return this text     public static Blah valueOfCode String blahCode  throws IllegalArgumentException       Blah blah   Arrays stream Blah values                 filter val - gt  val name   equals blahCode                findFirst                orElseThrow    - gt  new IllegalArgumentException  quot Unable to resolve blah    quot    blahCode         return blah

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Here s a nifty utility I use          A common method for all enums since they can t have another base class     param  lt T gt  Enum type     param c enum type  All enums must be all caps      param string case insensitive     return corresponding enum  or null     public static  lt T extends Enum lt T gt  gt  T getEnumFromString Class lt T gt  c  String string        if  c    null  amp  amp  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

User · Answer

Adding on to the top rated answer  with a helpful utility     valueOf   throws two different Exceptions in cases where it doesn t like its input    IllegalArgumentException NullPointerExeption   If your requirements are such that you don t have any guarantee that your String will definitely match an enum value  for example if the String data comes from a database and could contain old version of the enum  then you ll need to handle these often     So here s a reusable method I wrote which allows us to define a default Enum to be returned if the String we pass doesn t match   private static  lt T extends Enum lt T gt  gt  T valueOf  String name   T defaultVal            try               return Enum valueOf defaultVal getDeclaringClass     name             catch  IllegalArgumentException   NullPointerException e                return defaultVal                    Use it like this   public enum MYTHINGS       THINGONE      THINGTWO    public static void main String    asd      valueOf  THINGTWO    MYTHINGS THINGONE    returns MYTHINGS THINGTWO   valueOf  THINGZERO    MYTHINGS THINGONE    returns MYTHINGS THINGONE

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Enum is very useful  I have been using Enum a lot to add a description for some fields in different languages  as the following example   public enum Status        ACT new String      Accepted                   REJ new String      Rejected                   PND new String      Pending                         ERR new String      Error                 SNT new String      Sent                    private String   status       public String getDescription String lang            return lang equals  en     status 0    status 1              Status String   status            this status   status            And then you can retrieve the description dynamically based in the language code passed to getDescription String lang  method  for example   String statusDescription   Status valueOf  ACT   getDescription  en

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If you don t want to write your own utility use Google s guava library   Enums getIfPresent Blah class   A     Unlike the built in java function it let s you check if A is present in Blah and doesn t throw an exception

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Another utility capturing in reverse way  Using a value which identify that Enum  not from its name   import java lang reflect Method  import java lang reflect Modifier  import java util EnumSet   public class EnumUtil                   Returns the  lt code gt Enum lt  code gt  of type  lt code gt enumType lt  code gt  whose a         public method return value of this Enum is         equal to  lt code gt valor lt  code gt   lt br  gt         Such method should be unique public  not final and static method         declared in Enum         In case of more than one method in match those conditions        its first one will be chosen                  param enumType         param value         return              public static  lt E extends Enum lt E gt  gt  E from Class lt E gt  enumType  Object value            String methodName   getMethodIdentifier enumType           return from enumType  value  methodName                         Returns the  lt code gt Enum lt  code gt  of type  lt code gt enumType lt  code gt  whose          public method  lt code gt methodName lt  code gt  return is         equal to  lt code gt value lt  code gt   lt br  gt                 param enumType         param value         param methodName         return             public static  lt E extends Enum lt E gt  gt  E from Class lt E gt  enumType  Object value  String methodName            EnumSet lt E gt  enumSet   EnumSet allOf enumType           for  E en   enumSet                try                   String invoke   enumType getMethod methodName  invoke en  toString                    if  invoke equals value toString                           return en                                  catch  Exception e                    return null                                  return null             private static String getMethodIdentifier Class lt   gt  enumType            Method   methods   enumType getDeclaredMethods            String name   null          for  Method method   methods                int mod   method getModifiers                if  Modifier isPublic mod   amp  amp   Modifier isStatic mod   amp  amp   Modifier isFinal mod                     name   method getName                    break                                  return name            Example   public enum Foo       ONE  eins    TWO  zwei    THREE  drei         private String value       private Foo String value            this value   value             public String getValue             return value            EnumUtil from Foo class   drei   returns Foo THREE  because it will use getValue to match  drei   which is unique public  not final and not static method in Foo  In case Foo has more than on public  not final and not static method  for example  getTranslate which returns  drei   the other method can be used  EnumUtil from Foo class   drei    getTranslate

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

Kotlin Solution

Examples related to java

Examples related to enums