code: public String optString(String key,String defaultValue){
  		LazyNode token=getOptionalFieldToken(key);
  		if(token==null)return defaultValue;
  		if(token.type==LazyNode.VALUE_NULL)return defaultValue;
  		return token.getStringValue();
  	}
docs: Returns the string value stored in this object for the given key.
  Returns the default value if there is no such key.
  
  @param key the name of the field on this object
  @param defaultValue the default value to return
  @return the requested string value or the default value if there was no such key