/**
     * <p>
     * This sets an attribute value for this element.  Any existing attribute
     * with the same name and namespace URI is removed.
     * </p>
     *
     * @param attribute <code>Attribute</code> to set
     * @return this element modified
     * @throws IllegalAddException if the attribute being added already has a
     *   parent or if the attribute namespace prefix collides with another
     *   namespace prefix on the element.
     */
    public Element setAttribute(Attribute attribute) {
        if (attribute.getParent() != null) {
            throw new IllegalAddException(this, attribute,
                "The attribute already has an existing parent \"" +
                attribute.getParent().getQualifiedName() + "\"");
        }

        // Performance optimizing flag to help determine if we need to
        // bother removing an old attribute
        boolean preExisting = false;

        // Verify the attribute's namespace prefix doesn't collide with
        // another attribute prefix or this element's prefix.
        // This is unfortunately pretty heavyweight but we don't need to do it
        // for attributes without a namespace, and a little testing shows no
        // real difference in build times anyway.
        String prefix = attribute.getNamespace().getPrefix();
        if (!prefix.equals("")) {
          String uri = attribute.getNamespace().getURI();
          if (prefix.equals(getNamespacePrefix()) &&
                !uri.equals(getNamespaceURI())) {
              throw new IllegalAddException(this, attribute,
                "The attribute namespace prefix \"" + prefix +
                "\" collides with the element namespace prefix");
          }
          if (additionalNamespaces != null && additionalNamespaces.size() > 0) {
              Iterator itr = additionalNamespaces.iterator();
              while (itr.hasNext()) {
                  Namespace ns = (Namespace) itr.next();
                  if (prefix.equals(ns.getPrefix()) &&
                        !uri.equals(ns.getURI())) {
                      throw new IllegalAddException(this, attribute,
                        "The attribute namespace prefix \"" + prefix +
                        "\" collides with a namespace declared by the element");
                  }
              }
          }
          if (attributes != null && attributes.size() > 0) {
              Iterator itr = attributes.iterator();
              while (itr.hasNext()) {
                  Attribute att = (Attribute)itr.next();
                  Namespace ns = att.getNamespace();
                  // Keep track if we have an existing attribute
                  if (attribute.getName().equals(att.getName()) &&
                        ns.getURI().equals(att.getNamespaceURI())) {
                      preExisting = true;
                  }

                  if (prefix.equals(ns.getPrefix()) &&
                        !uri.equals(ns.getURI())) {
                      throw new IllegalAddException(this, attribute,
                          "The attribute namespace prefix \"" + prefix +
                          "\" collides with another attribute namespace on " +
                          "the element");
                  }
              }
          }
        }
        else{
          if (attributes != null && attributes.size() > 0) {
              Iterator itr = attributes.iterator();
              while (itr.hasNext()) {
                  Attribute att = (Attribute)itr.next();
                  // Keep track if we have an existing attribute
                  if (attribute.getName().equals(att.getName())) {
                      preExisting = true;
                      break;
                  }
              }
          }

        }

        if (attributes == null) {
            attributes = new ArrayList(INITIAL_ARRAY_SIZE);
        }
        else if (preExisting) {
            // Remove any pre-existing attribute
            removeAttribute(attribute.getName(), attribute.getNamespace());
        }

        attributes.add(attribute);
        attribute.setParent(this);
        return this;
    }