Java String.split() Regex

Question

I have a string:

String str = "a + b - c * d / e < f > g >= h <= i == j"; 

I want to split the string on all of the operators, but include the operators in the array, so the resulting array looks like:

[a , +,  b , -,  c , *,  d , /,  e , <,  f , >,  g , >=,  h , <=,  i , ==,  j] 

I've got this currently:

public static void main(String[] args) {     String str = "a + b - c * d / e < f > g >= h <= i == j";     String reg = "((?<=[<=|>=|==|\\+|\\*|\\-|<|>|/|=])|(?=[<=|>=|==|\\+|\\*|\\-|<|>|/|=]))";      String[] res = str.split(reg);     System.out.println(Arrays.toString(res)); } 

This is pretty close, it gives:

[a , +,  b , -,  c , *,  d , /,  e , <,  f , >,  g , >, =,  h , <, =,  i , =, =,  j] 

Is there something I can do to this to make the multiple character operators appear in the array like I want them to?

And as a secondary question that isn't nearly as important, is there a way in the regex to trim the whitespace off from around the letters?

Answer 1

String[] ops = str.split("\\s*[a-zA-Z]+\\s*"); String[] notops = str.split("\\s*[^a-zA-Z]+\\s*"); String[] res = new String[ops.length+notops.length-1]; for(int i=0; i<res.length; i++) res[i] = i%2==0 ? notops[i/2] : ops[i/2+1]; 

This should do it. Everything nicely stored in res.