Added the initi method also to FixedStepHandler.

Jira: MATH-714

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1207066 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/math/ode/sampling/FixedStepHandler.java

@@ -39,6 +39,18 @@ package org.apache.commons.math.ode.sampling;
 
 public interface FixedStepHandler  {
 
+  /** Initialize step handler at the start of an ODE integration.
+   * <p>
+   * This method is called once at the start of the integration. It
+   * may be used by the step handler to initialize some internal data
+   * if needed.
+   * </p>
+   * @param t0 start value of the independent <i>time</i> variable
+   * @param y0 array containing the start value of the state vector
+   * @param t target time for the integration
+   */
+  void init(double t0, double[] y0, double t);
+
   /**
    * Handle the last accepted step
    * @param t time of the current step

src/main/java/org/apache/commons/math/ode/sampling/StepNormalizer.java

@@ -174,11 +174,16 @@ public class StepNormalizer implements StepHandler {
 
     /** {@inheritDoc} */
     public void init(double t0, double[] y0, double t) {
+
         firstTime       = Double.NaN;
         lastTime        = Double.NaN;
         lastState       = null;
         lastDerivatives = null;
         forward         = true;
+
+        // initialize the underlying handler
+        handler.init(t0, y0, t);
+
     }
 
     /**

src/test/java/org/apache/commons/math/ode/sampling/StepNormalizerOutputTestBase.java

@@ -12,8 +12,8 @@ import org.junit.Test;
 
 /** Base class for step normalizer output tests. */
 public abstract class StepNormalizerOutputTestBase
-    implements FirstOrderDifferentialEquations, FixedStepHandler
-{
+    implements FirstOrderDifferentialEquations, FixedStepHandler {
+
     /** The normalized output time values. */
     private List<Double> output;
 
@@ -211,8 +211,13 @@ public abstract class StepNormalizerOutputTestBase
         yDot[0] = y[0];
     }
 
+    /** {@inheritDoc} */
+    public void init(double t0, double[] y0, double t) {
+    }
+
     /** {@inheritDoc} */
     public void handleStep(double t, double[] y, double[] yDot, boolean isLast) {
         output.add(t);
     }
+
 }

src/test/java/org/apache/commons/math/ode/sampling/StepNormalizerTest.java

@@ -41,7 +41,9 @@ public class StepNormalizerTest {
     setLastSeen(false);
     integ.addStepHandler(new StepNormalizer(range / 10.0,
                                        new FixedStepHandler() {
-                                        private boolean firstCall = true;
+                                         private boolean firstCall = true;
+                                         public void init(double t0, double[] y0, double t) {
+                                         }
                                          public void handleStep(double t,
                                                                 double[] y,
                                                                 double[] yDot,
@@ -69,7 +71,9 @@ public class StepNormalizerTest {
     setLastSeen(false);
     integ.addStepHandler(new StepNormalizer(range / 10.5,
                                        new FixedStepHandler() {
-                                        public void handleStep(double t,
+                                         public void init(double t0, double[] y0, double t) {
+                                         }
+                                         public void handleStep(double t,
                                                                 double[] y,
                                                                 double[] yDot,
                                                                 boolean isLast) {