title: Mutable method parameters in Scala
body: <p>Simple problem: I am subclassing a FilterInputStream in Scala, which has a read method:</p>
  
  <pre><code>public void read(byte [] b,int offset,int len)
  </code></pre>
  
  <p>The data being read will be put in b, but as parameters are "vals" in Scala methods, I see no way to properly subclass this. How do I set b to the data being read? The Java *InputStream really leaves me not much choice....</p>