Category "numberformatexception"

What is a NumberFormatException and how can I fix it?

Error Message: Exception in thread "main" java.lang.NumberFormatException: For input string: "Ace of Clubs" at java.lang.NumberFormatException.forInputStrin

Getting "NumberFormatException" input string="" error and I don't know how to solve it [duplicate]

I'm trying to solve this question, but the NumberFormatException always happens. Using try-catch doesn't give me what I want because it always