commons-file/src/main/java/info/monitorenter/cpdetector/io/ClassFileFilterIsA.java
public synchronized boolean addSuperClass(Class c) {
    boolean ret = false;
    if ((c.getModifiers() & Modifier.FINAL) != 0) {
    }
    else {
      ret = this.superclasses.add(c);
    }
    return ret;
  }
public synchronized boolean addSuperClass(Class c) {
    boolean ret = false;
    if ((c.getModifiers() & Modifier.FINAL) != 0) {
    }
    else {
      ret = this.superclasses.add(c);
    }
    return ret;
  }
<p>
Adds the given argument to the acceptance filter. The filter will only
return true for a Class a in the following condition:

<pre>
(a instanceof c)
</pre>

<p>
This method may be called several times. The accept method will return true
if the given Class is derived from any of the internal super classes.
</p>

@param c
A non-final Class.
@return true, if the given class could be added. It is not added, if
argument c is final (makes no sense as a final class is never a
superclass) or the given Class was already contained.