In Java how to find if first character in a string is upper case without regex

Question

In Java  find if the first character in a string is upper case without using regular expressions

User · Answer

There is many ways to do that  but the simplest seems to be the following one   boolean isUpperCase   Character isUpperCase  My String  charAt 0

User · Answer

String yourString    yadayada   if  Character isUpperCase yourString charAt 0             print something   else          print something else

User · Answer

we can find upper case letter by using regular expression as well  private static void findUppercaseFirstLetterInString String content        Matcher m   Pattern              compile    a-z    a-z      Pattern CASE INSENSITIVE  matcher                      content       System out println  Given input string       content       while  m find              if  m group 1  equals m group 1  toUpperCase                   System out println  First Letter Upper case match found                          m group                         for detailed example   please visit http   www onlinecodegeek com 2015 09 how-to-determines-if-string-starts-with html

User · Answer

Make sure you first check for null and empty and ten converts existing string to upper  Use S O P if want to see outputs otherwise boolean like Rabiz did    public static void main String   args          System out println  Enter name         Scanner kb   new Scanner  System in        String text    kb next          if   null    text    text isEmpty                    System out println  Text empty                else if  text charAt 0      text toUpperCase   charAt 0                    System out println  First letter in word    text     is upper case

User · Answer

If you have to check it out manually you can do int a   s charAt 0    If the value of a is between 65 to 90 it is upper case

User · Answer

Don t forget to check whether the string is empty or null  If we forget checking null or empty then we would get NullPointerException or StringIndexOutOfBoundException if a given String is null or empty    public class StartWithUpperCase           public static void main String   args                String str1         StringIndexOfBoundException if                                  empty checking not handled             String str2   null    NullPointerException if                                    null checking is not handled              String str3    Starts with upper case               String str4    starts with lower case                System out println startWithUpperCase str1      false             System out println startWithUpperCase str2      false             System out println startWithUpperCase str3      true             System out println startWithUpperCase str4      false                       public static boolean startWithUpperCase String givenString                if null    givenString    givenString isEmpty     return false              else return  Character isUpperCase  givenString codePointAt 0

User · Answer

Actually  this is subtler than it looks   The code above would give the incorrect answer for a lower case character whose code point was above U FFFF  such as U 1D4C3  MATHEMATICAL SCRIPT SMALL N   String charAt would return a UTF-16 surrogate pair  which is not a character  but rather half the character  so to speak  So you have to use String codePointAt  which returns an int above 0xFFFF  not a char   You would do   Character isUpperCase s codePointAt 0     Don t feel bad overlooked this  almost all Java coders handle UTF-16 badly  because the terminology misleadingly makes you think that each  char  value represents a character  UTF-16 sucks  because it is almost fixed width but not quite  So non-fixed-width edge cases tend not to get tested  Until one day  some document comes in which contains a character like U 1D4C3  and your entire system blows up

User · Answer

Assuming s is non-empty   Character isUpperCase s charAt 0     or  as mentioned by divec  to make it work for characters with code points above U FFFF   Character isUpperCase s codePointAt 0

[java] In Java, how to find if first character in a string is upper case without regex

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