title: Regular expression for arithmetic expression
body: <p>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...</p>
  
  <p>Only + and * operators.</p>
  
  <p>I tried </p>
  
  <p><code>if (str.matches("(\\d|\\w \\+|\\*){1,} \\d|\\w"))</code></p>
  
  <p>Unfortunately it only handles cases like  3 * 7  ... (numeric * numeric).</p>
  
  <p>Waiting for your answers, thanks for reading me.</p>