private constructors

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1897670 13f79535-47bb-0310-9956-ffa450edef68

poi/src/main/java/org/apache/poi/ss/formula/functions/NormDist.java

@@ -41,6 +41,8 @@ public final class NormDist extends Fixed4ArgFunction implements FreeRefFunction
         return cumulative ? normalDistribution.cumulativeProbability(x) : normalDistribution.density(x);
     }
 
+    private NormDist() {}
+
     @Override
     public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg1, ValueEval arg2,
                               ValueEval arg3, ValueEval arg4) {

poi/src/main/java/org/apache/poi/ss/formula/functions/NormInv.java

@@ -41,6 +41,8 @@ public final class NormInv extends Fixed3ArgFunction implements FreeRefFunction
         return normalDistribution.inverseCumulativeProbability(probability);
     }
 
+    private NormInv() {}
+
     @Override
     public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg1, ValueEval arg2, ValueEval arg3) {
         try {

poi/src/main/java/org/apache/poi/ss/formula/functions/NormSDist.java

@@ -35,6 +35,8 @@ public final class NormSDist extends Fixed1ArgFunction implements FreeRefFunctio
 
     public static final NormSDist instance = new NormSDist();
 
+    private NormSDist() {}
+
     @Override
     public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg1) {
         try {

poi/src/main/java/org/apache/poi/ss/formula/functions/NormSInv.java

@@ -35,6 +35,8 @@ public final class NormSInv extends Fixed1ArgFunction implements FreeRefFunction
 
     public static final NormSInv instance = new NormSInv();
 
+    private NormSInv() {}
+
     @Override
     public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg1) {
         try {

poi/src/main/java/org/apache/poi/ss/formula/functions/NumberValueFunction.java

@@ -37,6 +37,8 @@ public final class NumberValueFunction implements FreeRefFunction {
 
     public static final FreeRefFunction instance = new NumberValueFunction();
 
+    private NumberValueFunction() {}
+
     @Override
     public ValueEval evaluate( ValueEval[] args, OperationEvaluationContext ec ) {