## Why is this an issue?

Character classes in regular expressions are a convenient way to match one of several possible characters by listing the allowed characters or ranges of characters. If a character class contains only one character, the effect is the same as just writing the character without a character class.

Thus, having only one character in a character class is usually a simple oversight that remained after removing other characters of the class.

### Noncompliant code example

    "a[b]c"
    "[\\^]"

### Compliant solution

    "abc"
    "\\^"
    "a[*]c" // Compliant, see Exceptions

### Exceptions

This rule does not raise when the character inside the class is a metacharacter. This notation is sometimes used to avoid escaping (e.g., `[.]{3}` to match three dots).