reintroduced modifiers needed for serialization.

checkstyle.xml

@@ -189,6 +189,11 @@
     <property name="onCommentFormat"  value="CHECKSTYLE\: resume DeclarationOrder"/>
     <property name="checkFormat"      value="DeclarationOrder"/>
   </module>
+  <module name="SuppressionCommentFilter">
+    <property name="offCommentFormat" value="CHECKSTYLE\: stop RedundantModifier"/>
+    <property name="onCommentFormat"  value="CHECKSTYLE\: resume RedundantModifier"/>
+    <property name="checkFormat"      value="RedundantModifier"/>
+  </module>
   <module name="SuppressionCommentFilter">
     <property name="offCommentFormat" value="CHECKSTYLE\: stop all"/>
     <property name="onCommentFormat" value="CHECKSTYLE\: resume all"/>

src/main/java/org/apache/commons/math4/ode/nonstiff/ClassicalRungeKuttaStepInterpolator.java

@@ -68,8 +68,11 @@ class ClassicalRungeKuttaStepInterpolator
      * interpolators by cloning an uninitialized model and latter initializing
      * the copy.
      */
-    ClassicalRungeKuttaStepInterpolator() {
+    // CHECKSTYLE: stop RedundantModifier
+    // the public modifier here is needed for serialization
+    public ClassicalRungeKuttaStepInterpolator() {
     }
+    // CHECKSTYLE: resume RedundantModifier
 
     /** Copy constructor.
      * @param interpolator interpolator to copy from. The copy is a deep

src/main/java/org/apache/commons/math4/ode/nonstiff/DormandPrince54StepInterpolator.java

@@ -97,7 +97,9 @@ class DormandPrince54StepInterpolator
    * prototyping design pattern to create the step interpolators by
    * cloning an uninitialized model and latter initializing the copy.
    */
-  DormandPrince54StepInterpolator() {
+  // CHECKSTYLE: stop RedundantModifier
+  // the public modifier here is needed for serialization
+  public DormandPrince54StepInterpolator() {
     super();
     v1 = null;
     v2 = null;
@@ -105,6 +107,7 @@ class DormandPrince54StepInterpolator
     v4 = null;
     vectorsInitialized = false;
   }
+  // CHECKSTYLE: resume RedundantModifier
 
   /** Copy constructor.
    * @param interpolator interpolator to copy from. The copy is a deep

src/main/java/org/apache/commons/math4/ode/nonstiff/DormandPrince853StepInterpolator.java

@@ -227,12 +227,15 @@ class DormandPrince853StepInterpolator
    * prototyping design pattern to create the step interpolators by
    * cloning an uninitialized model and latter initializing the copy.
    */
-  DormandPrince853StepInterpolator() {
+  // CHECKSTYLE: stop RedundantModifier
+  // the public modifier here is needed for serialization
+  public DormandPrince853StepInterpolator() {
     super();
     yDotKLast = null;
     v         = null;
     vectorsInitialized = false;
   }
+  // CHECKSTYLE: resume RedundantModifier
 
   /** Copy constructor.
    * @param interpolator interpolator to copy from. The copy is a deep

src/main/java/org/apache/commons/math4/ode/nonstiff/EulerStepInterpolator.java

@@ -59,8 +59,11 @@ class EulerStepInterpolator
    * to create the step interpolators by cloning an uninitialized model
    * and later initializing the copy.
    */
-  EulerStepInterpolator() {
+  // CHECKSTYLE: stop RedundantModifier
+  // the public modifier here is needed for serialization
+  public EulerStepInterpolator() {
   }
+  // CHECKSTYLE: resume RedundantModifier
 
   /** Copy constructor.
    * @param interpolator interpolator to copy from. The copy is a deep

src/main/java/org/apache/commons/math4/ode/nonstiff/GillStepInterpolator.java

@@ -75,8 +75,11 @@ class GillStepInterpolator
    * to create the step interpolators by cloning an uninitialized model
    * and later initializing the copy.
    */
-  GillStepInterpolator() {
+  // CHECKSTYLE: stop RedundantModifier
+  // the public modifier here is needed for serialization
+  public GillStepInterpolator() {
   }
+  // CHECKSTYLE: resume RedundantModifier
 
   /** Copy constructor.
    * @param interpolator interpolator to copy from. The copy is a deep

src/main/java/org/apache/commons/math4/ode/nonstiff/GraggBulirschStoerStepInterpolator.java

@@ -107,13 +107,16 @@ class GraggBulirschStoerStepInterpolator
    * This constructor should not be used directly, it is only intended
    * for the serialization process.
    */
-  GraggBulirschStoerStepInterpolator() {
+    // CHECKSTYLE: stop RedundantModifier
+    // the public modifier here is needed for serialization
+  public GraggBulirschStoerStepInterpolator() {
     y0Dot    = null;
     y1       = null;
     y1Dot    = null;
     yMidDots = null;
     resetTables(-1);
   }
+  // CHECKSTYLE: resume RedundantModifier
 
   /** Simple constructor.
    * @param y reference to the integrator array holding the current state

src/main/java/org/apache/commons/math4/ode/nonstiff/HighamHall54StepInterpolator.java

@@ -45,9 +45,12 @@ class HighamHall54StepInterpolator
    * to create the step interpolators by cloning an uninitialized model
    * and later initializing the copy.
    */
-  HighamHall54StepInterpolator() {
+  // CHECKSTYLE: stop RedundantModifier
+  // the public modifier here is needed for serialization
+  public HighamHall54StepInterpolator() {
     super();
   }
+  // CHECKSTYLE: resume RedundantModifier
 
   /** Copy constructor.
    * @param interpolator interpolator to copy from. The copy is a deep

src/main/java/org/apache/commons/math4/ode/nonstiff/LutherStepInterpolator.java

@@ -51,8 +51,11 @@ class LutherStepInterpolator extends RungeKuttaStepInterpolator {
      * to create the step interpolators by cloning an uninitialized model
      * and later initializing the copy.
      */
-    LutherStepInterpolator() {
+    // CHECKSTYLE: stop RedundantModifier
+    // the public modifier here is needed for serialization
+    public LutherStepInterpolator() {
     }
+    // CHECKSTYLE: resume RedundantModifier
 
     /** Copy constructor.
      * @param interpolator interpolator to copy from. The copy is a deep

src/main/java/org/apache/commons/math4/ode/nonstiff/MidpointStepInterpolator.java

@@ -61,8 +61,11 @@ class MidpointStepInterpolator
    * to create the step interpolators by cloning an uninitialized model
    * and later initializing the copy.
    */
-  MidpointStepInterpolator() {
+  // CHECKSTYLE: stop RedundantModifier
+  // the public modifier here is needed for serialization
+  public MidpointStepInterpolator() {
   }
+  // CHECKSTYLE: resume RedundantModifier
 
   /** Copy constructor.
    * @param interpolator interpolator to copy from. The copy is a deep

src/main/java/org/apache/commons/math4/ode/nonstiff/ThreeEighthesStepInterpolator.java

@@ -71,8 +71,11 @@ class ThreeEighthesStepInterpolator
    * to create the step interpolators by cloning an uninitialized model
    * and later initializing the copy.
    */
-  ThreeEighthesStepInterpolator() {
+  // CHECKSTYLE: stop RedundantModifier
+  // the public modifier here is needed for serialization
+  public ThreeEighthesStepInterpolator() {
   }
+  // CHECKSTYLE: resume RedundantModifier
 
   /** Copy constructor.
    * @param interpolator interpolator to copy from. The copy is a deep