User input boundary - Java
<p>I'm quite new to programming. I am looking for a way to set a boundary for the user input variables. Here is a snippet of my code</p>

<pre><code>   public static void main(String[] agrs){

   Scanner user_input = new Scanner(System.in);

    String angle;
    System.out.println("Angle:");
    angle = user_input.next();
</code></pre>

<p>For example, I would like the possible input to be only between 30 and 60 degrees. </p>