How to use null in switch

Question

Integer i        switch  i       case null          doSomething0            break              In the code above I cant use null in switch case statement  How can I do this differently  I can t use default because then I want to do something else

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switch i  will throw a NullPointerException if i is null  because it will try to unbox the Integer into an int  So case null  which happens to be illegal  would never have been reached anyway   You need to check that i is not null before the switch statement

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You can t  You can use primitives  int  char  short  byte  and String  Strings in java 7 only  in switch  primitives can t be null  Check i in separate condition before switch

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switch   i    null    i   DEFAULT VALUE

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Based on  tetsuo answer  with java 8     Integer i        switch  Optional ofNullable i  orElse DEFAULT VALUE         case DEFAULT VALUE          doDefault            break

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Just consider how the SWITCH might work     in case of primitives we know it can fail with NPE for auto-boxing but for String or enum  it might be invoking equals method  which obviously needs a LHS value on which equals is being invoked  So  given no method can be invoked on a null  switch cant handle null

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This is not possible with a switch statement in Java  Check for null before the switch   if  i    null        doSomething0      else       switch  i        case 1                         break            You can t use arbitrary objects in switch statements   The reason that the compiler doesn t complain about switch  i  where i is an Integer is because Java auto-unboxes the Integer to an int  As assylias already said  the unboxing will throw a NullPointerException when i is null     Since Java 7 you can use String in switch statements   More about switch  including example with null variable  in Oracle Docs - Switch

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Given   public enum PersonType       COOL GUY 1       JERK 2        private final int typeId      private PersonType int typeId            this typeId   typeId             public final int getTypeId             return typeId             public static PersonType findByTypeId int typeId            for  PersonType type   values                  if  type typeId    typeId                    return type                                  return null            For me  this typically aligns with a look-up table in a database  for rarely-updated tables only    However  when I try to use findByTypeId in a switch statement  from  most likely  user input      int userInput   3  PersonType personType   PersonType findByTypeId userInput   switch personType    case COOL GUY         Do things only a cool guy would do      break  case JERK         Push back  Don t enable him      break  default         I don t know or care what to do with this mess         as others have stated  this results in an NPE   switch personType     One work-around  i e    solution   I started implementing was to add an UNKNOWN -1  type   public enum PersonType       UNKNOWN -1       COOL GUY 1       JERK 2               public static PersonType findByTypeId int id                        return UNKNOWN            Now  you don t have to do null-checking where it counts and you can choose to  or not to  handle UNKNOWN types   NOTE  -1 is an unlikely identifier in a business scenario  but obviously choose something that makes sense for your use-case

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Java docs clearly stated that   The prohibition against using null as a switch label prevents one from writing code that can never be executed  If the switch expression is of a reference type  such as a boxed primitive type or an enum  a run-time error will occur if the expression evaluates to null at run-time   You must have to verify for null before Swithch statement execution    if  i    null    See The Switch Statement  case null     will never be executed  therefore disallowed

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You can also use String valueOf  Object  nullableString   like  switch  String valueOf  Object  nullableString     case  someCase                break      case  null      or default                    break         See interesting SO Q A  Why does String valueOf null  throw a NullPointerException

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switch  String valueOf value        case  null       default

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Some libraries attempt to offer alternatives to the builtin java switch statement  Vavr is one of them  they generalize it to pattern matching   Here is an example from their documentation   String s   Match i  of      Case   1    one        Case   2    two        Case                You can use any predicate  but they offer many of them out of the box  and   null  is perfectly legal  I find this a more elegant solution than the alternatives  but this requires java8 and a dependency on the vavr library

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You have to make a   if  i    null       doSomething0      else      switch  i

[java] How to use null in switch

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