How can tokenize this string in java?

Question

How can I split these simple mathematical expressions into seperate strings?

I know that I basically want to use the regular expression: \"[0-9]+|[*+-^()]\"

Answer 1

Here's a short Java program that tokenizes such strings. If you're looking for evaluation of expression I can (shamelessly) point you at this post: An Arithemetic Expressions Solver in 64 Lines

  import java.util.ArrayList;
  import java.util.List;

  public class Tokenizer {
     private String input;

     public Tokenizer(String input_) { input = input_.trim(); }

     private char peek(int i) {
        return i >= input.length() ? '\0' : input.charAt(i);
     }

     private String consume(String... arr) {
        for(String s : arr)
           if(input.startsWith(s))
              return consume(s.length());
        return null;
     }

     private String consume(int numChars) {
        String result = input.substring(0, numChars);
        input = input.substring(numChars).trim();
        return result;
     }

     private String literal() {
        for (int i = 0; true; ++i)
           if (!Character.isDigit(peek(i)))
              return consume(i);
     }

     public List tokenize() {
        List res = new ArrayList();
        if(input.isEmpty())
           return res;

        while(true) {
           res.add(literal());
           if(input.isEmpty())
              return res;

           String s = consume("+", "-", "/", "*", "^");
           if(s == null)
              throw new RuntimeException("Syntax error " + input);
           res.add(s);
        }
     }

     public static void main(String[] args) {
        Tokenizer t = new Tokenizer("578+223-5^2");
        System.out.println(t.tokenize());
     }   
  }