What is the best way to tell if a character is a letter or number in Java without using regexes

Question

What is the best and or easiest way to recognize if a string charAt index  is an A-z letter or a number in Java without using regular expressions  Thanks

User · Accepted Answer

Character isDigit string charAt index    JavaDoc  will return true if it s a digit Character isLetter string charAt index    JavaDoc  will return true if it s a letter

User · Answer

import java util Scanner   public class v   public static void main String args      Scanner in new Scanner System in       String str      int l      int flag 0      System out println  Enter the String         str in nextLine        str str toLowerCase        str str replaceAll    s           char   ch str toCharArray        l str length        for int i 0 i lt l i             if   ch i   gt    a   amp  amp  ch i  lt    z       ch i   gt    A   amp  amp  ch i   lt    Z             flag 0                    else          flag            break             if flag  0      System out println  Onlt char

User · Answer

check if ch is a letter if   ch  gt    a   amp  amp  ch  lt    z       ch  gt    A   amp  amp  ch  lt    Z                   check if ch is a digit if  ch  gt    0   amp  amp  ch  lt    9                  check if ch is a whitespace if   ch             ch     n       ch      t                 Source  https   docs oracle com javase tutorial i18n text charintro html

User · Answer

Java Character class has an isLetterOrDigit method since version 1 0 2

User · Answer

I m looking for a function that checks only if it s one of the Latin letters or a decimal number  Since char c   255  which in printable version is   and considered as a letter by Character isLetter c   This function I think is what most developers are looking for   private static boolean isLetterOrDigit char c        return  c  gt    a   amp  amp  c  lt    z                  c  gt    A   amp  amp  c  lt    Z                  c  gt    0   amp  amp  c  lt    9

User · Answer

As the answers indicate  if you examine them carefully    your question is ambiguous   What do you mean by  an A-z letter  or a digit    If you want to know if a character is a Unicode letter or digit  then use the Character isLetter and Character isDigit methods  If you want to know if a character is an ASCII letter or digit  then the best thing to do is to test by comparing with the character ranges  a  to  z    A  to  Z  and  0  to  9     Note that all ASCII letters   digits are Unicode letters   digits     but there are many Unicode letters   digits characters that are not ASCII   For example  accented letters  cyrillic  sanskrit         The general solution is to do this   Character UnicodeBlock block   Character UnicodeBlock of someCodePoint     and then test to see if the block is one of the ones that you are interested in   In some cases you will need to test for multiple blocks   For example  there are  at least  4 code blocks for Cyrillic characters and 7 for Latin   The Character UnicodeBlock class defines static constants for well-known blocks  see the javadocs   Note that any code point will be in at most one block

User · Answer

Compare its value  It should be between the value of  a  and  z    A  and  Z    0  and  9

User · Answer

Use the below code   Character isLetterOrDigit string charAt index

User · Answer

I don t know about best  but this seems pretty simple to me   Character isDigit str charAt index   Character isLetter str charAt index

[java] What is the best way to tell if a character is a letter or number in Java without using regexes?

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