Figuring out whether a number is a Double in Java

Question

I m a Java newbie  I m trying to figure out whether a number is a Double with something like this   if   typeof   items elementAt 1      Double            sum add  i  items elementAt 1        Would appreciate if someone could tell me how to rearrange the syntax to make this work properly

User · Answer

Since this is the first question from Google I ll add the JavaScript style typeof alternative here as well   myObject getClass   getName      String

User · Answer

Use regular expression to achieve this task  Please refer the below code   public static void main String   args        try            BufferedReader reader   new BufferedReader new InputStreamReader System in            System out print  Enter your content              String data   reader readLine                        boolean b1   Pattern matches     d     data           boolean b2   Pattern matches   0-9a-zA-Z   -    d       d       data            boolean b3   Pattern matches      -    d       d      data           if b1                System out println  It is integer               else if b2                System out println  It is String                else if b3                System out println  It is Float                                 catch  IOException ex            Logger getLogger TypeOF class getName    log Level SEVERE  null  ex

User · Answer

Reflection is slower  but works for a situation when you want to know whether that is of type Dog or a Cat and not an instance of Animal  So you d do something like   if null    items elementAt 1   amp  amp  items elementAt 1  getClass   toString   equals  Cat        do whatever with cat   not any other instance of animal   eg  hideClaws        Not saying the answer above does not work  except the null checking part is necessary   Another way to answer that is use generics and you are guaranteed to have Double as any element of items   List lt Double gt  items   new ArrayList lt Double gt

User · Answer

Try this   if  items elementAt 1  instanceof Double       sum add  i  items elementAt 1

[java] Figuring out whether a number is a Double in Java

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