正则表达式在运算符之后拆分数学表达式并查找负数

Question

Is there someway to split an expression according to operators and negative numbers?

if I have a string "2+-2" , I want the -2 to be the object in my array?

    String exp = "2+-2";
    String[] temp = new String[exp.length()];
    temp =exp.split("(?<=[-+*/^])|(?=[-+*/^])");
    Stack<String> stack = new Stack<String>();
    LinkedList <String>list= new LinkedList<String>();
    for (int i=0; i<temp.length; i++) {
        String s = temp[i]+"";
        if(s.equals("-")) {
           while(!stack.isEmpty())
           {
              String tkn=stack.pop();
              if(tkn.equals("*")|| tkn.equals("/") || tkn.equals("+")||tkn.equals("-")||tkn.equals("^"))
                  list.add(tkn);
              else{
                  stack.push(tkn);
                  break;
              }
           }
           stack.push(s);
. . . for every operator . . .

Answer 1

Description

This regex will:

• Find all the numbers in a math equation
• Capture all numbers and return them as an array
• Capture the positive or negative sign if included on a number

Regex

(?:(?<=[-+/*^]|^)[-+])?\d+(?:[.]\d+)?

Example

Sample Java Code

import java.util.regex.Pattern;
import java.util.regex.Matcher;
class Module1{
  public static void main(String[] asd){
  String sourcestring = "source string to match with pattern";
  Pattern re = Pattern.compile("(?:(?<=[-+/*^])[-+]?)\\d+(?:[.]\\d+)?",Pattern.CASE_INSENSITIVE | Pattern.DOTALL);
  Matcher m = re.matcher(sourcestring);
  int mIdx = 0;
    while (m.find()){
      for( int groupIdx = 0; groupIdx < m.groupCount()+1; groupIdx++ ){
        System.out.println( "[" + mIdx + "][" + groupIdx + "] = " + m.group(groupIdx));
      }
      mIdx++;
    }
  }
}

Sample Text

1+1
2.1+-2.2
3.1+3.2
4.1--4.2
5.1-+5.2
-6.1--6.2
7.1-7.2

Capture Groups

[0] => 1
[1] => 1
[2] => 2.1
[3] => -2.2
[4] => 3.1
[5] => 3.2
[6] => 4.1
[7] => -4.2
[8] => 5.1
[9] => +5.2
[10] => 6.1
[11] => -6.2
[12] => 7.1
[13] => 7.2

Online Java Validator

http://fiddle.re/b2w5wa

Extra

In your original question you eluded to only being interested in the second value. If that is the case then this is the regex for you

(?:(?<=[-+/*^])[-+]?)\d+(?:[.]\d+)?

Capture Groups

[0] => 1
[1] => -2.2
[2] => 3.2
[3] => -4.2
[4] => +5.2
[5] => 6.1
[6] => -6.2
[7] => 7.2