Null Object Pattern

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In object-oriented computer programming, a Null Object is an object with defined neutral ("null") behavior. The Null Object design pattern describes the uses of such objects and their behavior (or lack thereof). It was first published in the Pattern Languages of Program Design book series.In most object-oriented languages, such as Java, references may be null. These references need to be checked to ensure they are not null before invoking any methods, because one can't invoke anything on a null reference.