Regex for checking if a string is strictly alphanumeric

Question

How can I check if a string contains only numbers and alphabets ie. is alphanumeric?

Answer 1

100% alphanumeric RegEx (it contains only alphanumeric, not even integers & characters, only alphanumeric)

For example:

special char (not allowed)
123 (not allowed)
asdf (not allowed)
1235asdf (allowed)

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String name="^[^]\\d*[a-zA-Z][a-zA-Z\\d]*$";