fixed findbugs errors

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@919855 13f79535-47bb-0310-9956-ffa450edef68

findbugs-exclude-filter.xml

@@ -108,6 +108,11 @@
     <Method name="&lt;init>" params="double[],double[][],boolean" returns="void" />
     <Bug pattern="EI_EXPOSE_REP2" />
   </Match>
+  <Match>
+    <Class name="org.apache.commons.math.ode.sampling.DummyStepInterpolator"/>
+    <Method name="&lt;init>" params="double[],double[],boolean" returns="void" />
+    <Bug pattern="EI_EXPOSE_REP2" />
+  </Match>
   <Match>
     <Class name="org.apache.commons.math.ode.sampling.AbstractStepInterpolator"/>
     <Or>

src/main/java/org/apache/commons/math/ode/jacobians/FirstOrderIntegratorWithJacobians.java

@@ -596,6 +596,12 @@ public class FirstOrderIntegratorWithJacobians {
         /** Time derivative of the jacobian with respect to parameters dy/dp. */
         private double[][] dydpDot;
 
+        /** Simple constructor.
+         * <p>This constructor is used only for externalization. It does nothing.</p>
+         */
+        public StepInterpolatorWrapper() {
+        }
+
         /** Simple constructor.
          * @param interpolator wrapped interpolator
          * @param n dimension of the original ODE