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:
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.
String tabInside = "A B"; // Noncompliant, contains a tabulation String zeroWidthSpaceInside = "foobar"; // Noncompliant, it contains a U+200B character inside char tab = ' ';
String tabInside = "A\tB"; // Compliant, uses escaped value String zeroWidthSpaceInside = "foo\u200Bbar"; // Compliant, uses escaped value char tab = '\t';
Text Blocks string literals (java 13 three double-quote marks) can contain tabulations to allow indentation using tabulations.