Check for a behavior change for an empty TreeSet add and TreeMap put methods

This rule flags the add method on the java.util.TreeSet class and the put method on the java.util.TreeMap class because their behavior has changed.

According to Java SE 7 and JDK 7 Compatibility documentation, the first attempt to insert a null object into empty TreeSet and TreeMap objects using the add() or put() methods now throws a java.lang.NullPointerException . In the previous implementation of the JDK, the first insertion of a null object using the add() or put() methods did not throw this exception. Attempting to insert a null to a non-empty TreeSet or TreeMap using these methods continues to fail with java.lang.NullPointerException as it did in previous JDK releases.

For additional information, see the Java 7 APIs:

• java.util.TreeSet Java documentation
• java.util.TreeMap Java documentation