regex for simple math equation

Question

I want to recognize integers or decimals and the four simple operations, broken into tokens I can\'t get the decimal to work, can you please help?

My reg is

Answer 1

It may works for you:

expression = "2.7 + 3 * (1 + 2)";
String expRegString = "\\d+(\\.\\d+)*|\\(\\d+(\\.\\d+)*[\\+\\-\\*\\/]\\d+(\\.\\d+)*\\)";

Answer 2

You can try removing all spaces and then split your data on every place that is before or after characters - + * / ( ).

This should do the trick

String expression = "2.7 + 3 * (1 + 2)";
String[] tokens = expression.replaceAll("\\s+", "").split("(?<=[-+*/()])|(?=[-+*/()])");

for (String token : tokens)
    System.out.println(token);

Output

2.7
+
3
*
(
1
+
2
)