如何使用正则表达式 Java 拆分此字符串

Question

As the title says I want to split a string specifically but I don´t know what to put inside the String.split("regex")

Say we have:

String s = "sum := A+B*( 99.1 +.44 444 1234+++)-sum/232.123459"

Now I want to split it to put it this way:

String[] splitted = ["sum"; ":="; "A"; "+"; "B"; "*"; "("; "99.1"; "+"; ".44"; "444"; "1234"; "+"; "+"; "+"; ")"; "-"; "sum"; "/"; "232.123459"]

So, basically I want to split by space, words, the math operators, numbers, the parenthesis, the letters and the number ".44" has to remain this way.

Can you help me? Thanks in advance

Answer 1

Don't use split() . Use a find() loop.

String regex = "[0-9]+\\.?[0-9]*" + // Match number (e.g. 999 or 999.99)
              "|\\.[0-9]+" +        // Match number (e.g. .999)
              "|[a-zA-Z]\\w*" +     // Match identifier
              "|:=" +  // Match complex operator
              "|\\S";  // Match other single non-space, incl. operators: +, -, *, /, (, )

Test

String s = "sum := A+B*( 99.1 +.44 444 1234+++)-sum/232.123459";
String[] splitted  = Pattern.compile(regex).matcher(s).results()
        .map(MatchResult::group).toArray(String[]::new);
System.out.println(Arrays.toString(splitted));

Output

[sum, :=, A, +, B, *, (, 99.1, +, .44, 444, 1234, +, +, +, ), -, sum, /, 232.123459]