NULL PATTERN
Developers often check for null whenever they get an Object from a 
method. This constant checking for null is a waste of developer time. 
Also, the code bloat can help lead to bugs.

To solve this, use the Null pattern to return an Object from the method 
instead of null.

Mark Grand introduced the Null pattern in his book, PATTERNS IN JAVA 
VOLUME 1 (ISBN 0-471-25839-3). The general idea is that rather than 
returning null from a method, an Object is returned that has no 
apparent behavior.

Examples:   return "" instead of null 
            return new ArrayList() instead of null 
            return NullCommand...

Further, you can make a marker interface named Null and set any class 
that exists to provide null behavior to implement Null. This improves 
the readability of code and allows an explanation of the Null pattern 
to be in the marker interface and not in every class that uses the 
pattern.

A marker interface is an interface with no method signatures. The 
example here is:

package com.generationjava.patterns; 
 
/** 
 * Implements the .... 
 */ 
public interface Null { 
}

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