code: public void setCollectionType( Class collectionType ) {
        if( collectionType != null ) {
           if( !Collection.class.isAssignableFrom( collectionType ) ) {
              throw new JSONException( "The configured collectionType is not a Collection: " + collectionType.getName() );
           }
           this.collectionType = collectionType;
        } else {
           collectionType = DEFAULT_COLLECTION_TYPE;
        }
     }
docs: Sets the current collection type used for collection transformations.<br>
  [JSON -&gt; Java]
  
  @param collectionType the target collection class for conversion