Added new rule

git-svn-id: https://pmd.svn.sourceforge.net/svnroot/pmd/trunk@1432 51baf565-9d33-0410-a72c-fc3788e3496d

pmd/rulesets/newrules.xml

@@ -5,6 +5,41 @@
 These are new rules for the next release
   </description>
 
+    <rule name="ConstructorCallsOverridableMethodRule"
+          message="Avoid calls to overridable methods during construction"
+          class="net.sourceforge.pmd.rules.ConstructorCallsOverridableMethodRule">
+      <description>
+      Calling overridable methods during construction poses a risk of invoking methods on an
+          incompletely constructed object.  This situation can be difficult to discern.
+      It may leave the sub-class unable to construct its superclass or forced to
+          replicate the construction process completely within itself, losing the ability to call
+      super().  If the default constructor contains a call to an overridable method,
+          the subclass may be completely uninstantiable.
+      </description>
+        <priority>3</priority>
+      <example>
+  <![CDATA[
+    public class SeniorClass {
+      public SeniorClass(){
+          toString(); //may throw NullPointerException if overridden
+      }
+      public String toString(){
+        return "IAmSeniorClass";
+      }
+    }
+    public class JuniorClass extends SeniorClass {
+      private String name;
+      public JuniorClass(){
+        super(); //Automatic call leads to NullPointerException
+        name = "JuniorClass";
+      }
+      public String toString(){
+        return name;
+      }
+    }
+  ]]>
+      </example>
+    </rule>
 
     <rule name="SymbolTableTestRule"
           message="test"