## Why is this an issue?

Non-encoded control characters and whitespace characters are often injected in the source code because of a bad manipulation. They are either invisible or difficult to recognize, which can result in bugs when the string is not what the developer expects. If you actually need to use a control character use their encoded version (ex: ASCII `\n,\t,`…​ or Unicode `U+000D, U+0009,`…​).

This rule raises an issue when the following characters are seen in a literal string:

- ASCII control character. (character index < 32 or = 127)
- Unicode whitespace characters.
- Unicode C0 control characters
- Unicode characters `U+200B, U+200C, U+200D, U+2060, U+FEFF, U+2028, U+2029`

No issue will be raised on the simple space character. Unicode `U+0020`, ASCII 32.

### Noncompliant code example

    String tabInside = "A	B";  // Noncompliant, contains a tabulation
    String zeroWidthSpaceInside = "foo​bar"; // Noncompliant, it contains a U+200B character inside
    char tab = '	';

### Compliant solution

    String tabInside = "A\tB";  // Compliant, uses escaped value
    String zeroWidthSpaceInside = "foo\u200Bbar";  // Compliant, uses escaped value
    char tab = '\t';