Regular expression for arithmetic expression

Question

I,m trying to write a regex to check if the given string is like a + b, 2 + a + b, 3 + 6 * 9 + 6 * 5 + a * b, etc...

Only + and * operators.

I tried

if (str.matches("(\\\\d|\\\\w \\\\+|\\\\*){1,} \\\\d|\\\\w"))

Unfortunately it only handles cases like 3 * 7 ... (numeric * numeric).

Waiting for your answers, thanks for reading me.

Answer 1

Put * and + inside a character class.

str.matches("\\w(?:\\s[+*]\\s\\w)+");

DEMO

Answer 2

This will handle cases of simple and chained calculations

[0-9A-Za-a]*( ){0,}([+-/*]( ){0,}[0-9A-Za-a]*( ){0,})*

This would match, for example

• 1+2
• 1 + 2
• 1 + a * 14 / 9

(You can change the operators you want by updating [+-/*] )