split, and the Dot That Consumes Everything

split takes a regular expression, not a plain separator, so splitting on an unescaped dot matches every character and leaves nothing behind. It fails quietly — no error, just an array that's wrong.

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Test data arrives in rows. split cuts a String into an array on a separator:

String row = "LoginTest,PASS,240";
String[] parts = row.split(",");

fields: 3
name  : LoginTest
status: PASS
ms    : 240

That is a CSV row parsed into fields, and combined with Chapter 7 you can turn each row into a TestResult object. It is also where a trap waits, and it catches nearly everyone once:

String path = "a.b.c";
System.out.println("dot split wrong: " + path.split(".").length);
System.out.println("dot split right: " + path.split("\\.").length);

dot split wrong: 0
dot split right: 3

Splitting on a dot returned zero fields. The reason is that split does not take a plain separator — it takes a regular expression, and in that language a dot means "any character." So the string was split on every character, leaving nothing behind. Escaping it as "\\." says "an actual dot" and produces the three fields you expected.

The characters that need escaping are the ones with special meaning in regular expressions: . | ( ) [ ] { } ^ $ * + ? \. A pipe-separated file split on "|" fails the same way, and it fails quietly — you get an empty or nonsensical array rather than an error.

One more edge worth knowing: by default split discards empty strings at the end of the result. A CSV row ending in two commas can therefore produce fewer fields than you expect. Pass a negative limit — row.split(",", -1) — to keep them, which matters when column positions must line up.

split cuts a row apart on a pattern. The same pattern language does more than cutting — it can also validate a whole value's shape, or strip everything that doesn't belong.