From 444c87274c0e7b921d26a455c1b8e9b5522e1f2e Mon Sep 17 00:00:00 2001
From: Phil Steitz <psteitz@apache.org>
Date: Sun, 6 Jun 2004 23:14:09 +0000
Subject: [PATCH] Cached DistributionFactory instance.

git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/math/trunk@141284 13f79535-47bb-0310-9956-ffa450edef68
---
 .../stat/inference/ChiSquareTestImpl.java     | 22 ++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/java/org/apache/commons/math/stat/inference/ChiSquareTestImpl.java b/src/java/org/apache/commons/math/stat/inference/ChiSquareTestImpl.java
index 41d8f2d80..2c2dc8197 100644
--- a/src/java/org/apache/commons/math/stat/inference/ChiSquareTestImpl.java
+++ b/src/java/org/apache/commons/math/stat/inference/ChiSquareTestImpl.java
@@ -15,8 +15,6 @@
  */
 package org.apache.commons.math.stat.inference;
 
-import java.io.Serializable;
-
 import org.apache.commons.math.MathException;
 import org.apache.commons.math.distribution.DistributionFactory;
 import org.apache.commons.math.distribution.ChiSquaredDistribution;
@@ -24,9 +22,12 @@ import org.apache.commons.math.distribution.ChiSquaredDistribution;
 /**
  * Implements Chi-Square test statistics defined in the {@link ChiSquareTest} interface.
  *
- * @version $Revision: 1.4 $ $Date: 2004/06/05 20:11:06 $
+ * @version $Revision: 1.5 $ $Date: 2004/06/06 23:14:09 $
  */
 public class ChiSquareTestImpl implements ChiSquareTest {
+    
+    /** Cached DistributionFactory used to create ChiSquaredDistribution instances */
+    private DistributionFactory distributionFactory = null;
   
     public ChiSquareTestImpl() {
         super();
@@ -67,7 +68,7 @@ public class ChiSquareTestImpl implements ChiSquareTest {
     public double chiSquareTest(double[] expected, long[] observed)
         throws IllegalArgumentException, MathException {
         ChiSquaredDistribution chiSquaredDistribution =
-            DistributionFactory.newInstance().createChiSquareDistribution((double) expected.length - 1);
+            getDistributionFactory().createChiSquareDistribution((double) expected.length - 1);
         return 1 - chiSquaredDistribution.cumulativeProbability(chiSquare(expected, observed));
     }
 
@@ -135,7 +136,7 @@ public class ChiSquareTestImpl implements ChiSquareTest {
         checkArray(counts);
         double df = ((double) counts.length -1) * ((double) counts[0].length - 1);
         ChiSquaredDistribution chiSquaredDistribution =
-            DistributionFactory.newInstance().createChiSquareDistribution(df);
+            getDistributionFactory().createChiSquareDistribution(df);
         return 1 - chiSquaredDistribution.cumulativeProbability(chiSquare(counts));
     }
 
@@ -183,6 +184,17 @@ public class ChiSquareTestImpl implements ChiSquareTest {
         
     }
     
+    //---------------------  Protected methods ---------------------------------
+    /**
+     * Gets a DistributionFactory to use in creating ChiSquaredDistribution instances.
+     */
+    protected DistributionFactory getDistributionFactory() {
+        if (distributionFactory == null) {
+            distributionFactory = DistributionFactory.newInstance();
+        }
+        return distributionFactory;
+    }
+    
     //---------------------  Private array methods -- should find a utility home for these
     
     /**