What is the exception to throw when the preprocessing method has not been called?

Question

I have a method getUserthat retrieves a user from a database. This method requires confirmation that the user really exists (using the method userExists(String username).

If the method getUseris called and the user does not exist, I want to throw an unchecked exception, but which exception is most suitable here? I thought about IllegalArgumentException, but it doesn’t feel completely right, because in some cases some inputs may be OK, but not others - they are not strictly “illegal”. Any suggestions?

Answer 1

IllegalArgumentException , . IllegalStateException, , .

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public class UsernameNotCheckedException extends IllegalStateException {
    public UsernameNotCheckedException(String message) {
        super(message);
    }
}

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A NumberFormatException IllegalArgumentException. 12QW4, NumberFormatException, . -.

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Answer 2

IllegalStateException . IllegalStateException , , .. this , , . this (.. ) , "".

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Answer 3

null. UserDoesNotExistException.

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