Java String Split() 方法

Question

I was wondering what the following line would do:

String parts = inputLine.split("\\s+");

Would this simply split the string at any spaces in the line? I think this a regex, but I've never seen them before.

Answer 1

Yes, as documentation states split takes regex as argument.

In regex \\s represents character class of containing whitespace characters like:

• tab \\t ,
• space " " ,
• line separators \\n \\r
• more...

+ is quantifier which can be read as " once or more " which makes \\s+ representing text build from one or more whitespaces.

We need to write this regex as "\\\\s+ (with two backslashes) because in String \\ is considered special character which needs escaping (with another backslash) to produce \\ literal.

So split("\\\\s+") will produce array of tokens separated by one or more whitespaces. BTW trailing empty elements are removed so "abc ".split("\\\\s+") will return array ["a", "b", "c"] not ["a", "b", "c", ""] .

Answer 2

Yes, though actually any number of space meta-characters (including tabs, newlines etc). See the Java documentation on Patterns .

Answer 3

It will split the string on one (or more) consecutive white space characters. The Pattern Javadoc describes the Predefined character classes (of which \\s is one) as,

Predefined character classes

. Any character (may or may not match line terminators) \\d A digit: [0-9] \\DA non-digit: [^0-9] \\s A whitespace character: [ \\t\\n\\x0B\\f\\r] \\SA non-whitespace character: [^\\s] \\w A word character: [a-zA-Z_0-9] \\WA non-word character: [^\\w]

Note that the \\\\ is to escape the back-slash as required to embed it in a String .

Answer 4

Yes, and it splits both tab and space:

String t = "test your   function      aaa";

for(String s : t.split("\\s+"))
   System.out.println(s);

Output:

 test your function aaa