Program to find whether a string is alphanumeric.

Any word that contains numbers and letters is known as alphanumeric. The following regular expression matches the combination of numbers and letters.

"^[a-zA-Z0-9]+$";

The matches method of the String class accepts a regular expression (in the form of a String) and matches it with the current string in case the match this method returns true else it returns false.

Therefore, to find whether a particular string contains alpha-numeric values −

• Get the string.
• Invoke the match method on it bypassing the above mentioned regular expression.
• Retrieve the result.

Example 1

import java.util.Scanner; public class AlphanumericString {    public static void main(String args[]) {       Scanner sc = new Scanner(System.in);       System.out.println("Enter input string: ");       String input = sc.next();       String regex = "^[a-zA-Z0-9]+$";       boolean result = input.matches(regex);       if(result) {          System.out.println("Given string is alpha numeric");       } else {          System.out.println("Given string is not alpha numeric");       }    } }

Output

Enter input string: abc123* Given string is not alpha numeric

Example 2

You can also compile a regular expression and match it with a particular string using the classes and methods (APIs) of the java.util.regex package. The following program is written using these APIs and it verifies whether a given string is alpha-numeric.

import java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class Test {    public static void main( String args[] ) {       Scanner sc = new Scanner(System.in);       System.out.println("Enter input string: ");       String input = sc.nextLine();       String regex = "^[a-zA-Z0-9]+$";       String data[] = input.split(" ");       //Creating a pattern object       Pattern pattern = Pattern.compile(regex);       for (String ele : data){          //creating a matcher object          Matcher matcher = pattern.matcher(ele);          if(matcher.matches()) {             System.out.println("The word "+ele+": is alpha numeric");          } else {             System.out.println("The word "+ele+": is not alpha numeric");          }       }    } }

Output

Enter input string: hello* this$ is sample text The word hello*: is not alpha numeric The word this$: is not alpha numeric The word is: is alpha numeric The word sample: is alpha numeric The word text: is alpha numeric