Best way to negate an instanceof

Question

I was thinking if there exists a better nicer way to negate an instanceof in Java  Actually  I m doing something like   if   str instanceof String        do Something        But I think that a  beautiful  syntax to do this should exist   Does anyone know if it exists  and how the syntax look like     EDIT  By beautiful  I might say something like this   if str  instanceof String       do Something         compilation fails

User · Accepted Answer

No  there is no better way  yours is canonical

User · Answer

I agree that in most cases the if    x instanceof Y         is the best approach  but in some cases creating an isY x  function so you can if   isY x         is worthwhile   I m a typescript novice  and I ve bumped into this S O question a bunch of times over the last few weeks  so for the googlers the typescript way to do this is to create a typeguard like this   typeGuards ts  export function isHTMLInputElement  value  any   value is HTMLInputElement     return value instanceof HTMLInputElement     usage  if   isHTMLInputElement x   throw new RangeError      do something with an HTMLInputElement   I guess the only reason why this might be appropriate in typescript and not regular js is that typeguards are a common convention  so if you re writing them for other interfaces  it s reasonable   understandable   natural to write them for classes too   There s more detail about user defined type guards like this in the docs

User · Answer

If you can use static imports  and your moral code allows them  public class ObjectUtils       private final Object obj      private ObjectUtils Object obj            this obj   obj             public static ObjectUtils thisObj Object obj           return new ObjectUtils obj              public boolean isNotA Class lt   gt  clazz           return  clazz isInstance obj             And then     import static notinstanceof ObjectUtils     public class Main        public static void main String   args            String a               if  thisObj a  isNotA String class                 System out println  It is not a String                      if  thisObj a  isNotA Integer class                 System out println  It is not an Integer                            This is just a fluent interface exercise  I d never use that in real life code  Go for your classic way  it won t confuse anyone else reading your code

User · Answer

If you find it more understandable  you can do something like this with Java 8     public static final Predicate lt Object gt  isInstanceOfTheClass        objectToTest - gt  objectToTest instanceof TheClass   public static final Predicate lt Object gt  isNotInstanceOfTheClass        isInstanceOfTheClass negate       or objectToTest - gt    objectToTest instanceof TheClass   if  isNotInstanceOfTheClass test myObject            do something

User · Answer

You can achieve by doing below way   just add a condition by adding bracket if   condition with instanceOf   with the whole condition by adding   operator at the start just the way mentioned in below code snippets   if   str instanceof String        do Something         COMPILATION WORK   instead of   if str  instanceof String       do Something         COMPILATION FAIL

User · Answer

I don t know what you imagine when you say  beautiful   but what about this  I personally think it s worse than the classic form you posted  but somebody might like it     if  str instanceof String    false

User · Answer

You could use the Class isInstance method   if  String class isInstance str        do Something            but it is still negated and pretty ugly

User · Answer

Usually you don t want just an if but an else clause as well   if   str instanceof String        do Something       else      do something else        can be written as  if str instanceof String       do Something else       else      do something        Or you can write the code so you don t need to know if its a String or not  e g   if   str instanceof String     str   str toString         can be written as  str   str toString

User · Answer

ok just my two cents  use a is string method   public static boolean isString Object thing        return thing instanceof String     public void someMethod Object thing       if   isString thing             return null            log debug  my thing is valid

[java] Best way to "negate" an instanceof

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