Add ability to build compound hashCode using superclass

git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/lang/trunk@137175 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/commons/lang/builder/HashCodeBuilder.java

@@ -80,7 +80,7 @@ import java.lang.reflect.Modifier;
  *   public int hashCode() {
  *     // you pick a hard-coded, randomly chosen, non-zero, odd number
  *     // ideally different for each class
- *     return new HashCodeBuilder(17, 37).   
+ *     return new HashCodeBuilder(17, 37).
  *       append(name).
  *       append(age).
  *       append(smoker).
@@ -88,6 +88,8 @@ import java.lang.reflect.Modifier;
  *   }
  * }
  * </pre>
+ * 
+ * <p>If required, the superclass hashCode can be added using {@link #appendSuper}.</p>
  *
  * <p>Alternatively, there is a method that uses reflection to determine
  * the fields to test. Because these fields are usually private, the method, 
@@ -104,7 +106,7 @@ import java.lang.reflect.Modifier;
  * </pre>
  * 
  * @author <a href="mailto:scolebourne@joda.org">Stephen Colebourne</a>
- * @version $Id: HashCodeBuilder.java,v 1.5 2002/11/17 21:46:42 scolebourne Exp $
+ * @version $Id: HashCodeBuilder.java,v 1.6 2002/12/08 21:22:07 scolebourne Exp $
  */
 public class HashCodeBuilder {
     
@@ -297,6 +299,19 @@ public class HashCodeBuilder {
 
     //-------------------------------------------------------------------------
     
+    /**
+     * <p>Adds the result of super.hashCode() to this builder.</p>
+     *
+     * @param superHashCode  the result of calling <code>super.hashCode()</code>
+     * @return this HashCodeBuilder, used to chain calls.
+     */
+    public HashCodeBuilder appendSuper(int superHashCode) {
+        iTotal = iTotal * iConstant + superHashCode;
+        return this;
+    }
+    
+    //-------------------------------------------------------------------------
+    
     /**
      * <p>Append a <code>hashCode</code> for an <code>Object</code>.</p>
      *

src/test/org/apache/commons/lang/builder/HashCodeBuilderTest.java

@@ -61,7 +61,7 @@ import junit.textui.TestRunner;
  * Unit tests {@link org.apache.commons.lang.HashCodeBuilder}.
  *
  * @author <a href="mailto:scolebourne@joda.org">Stephen Colebourne</a>
- * @version $Id: HashCodeBuilderTest.java,v 1.1 2002/09/12 22:01:00 scolebourne Exp $
+ * @version $Id: HashCodeBuilderTest.java,v 1.2 2002/12/08 21:22:42 scolebourne Exp $
  */
 public class HashCodeBuilderTest extends TestCase {
 
@@ -166,6 +166,13 @@ public class HashCodeBuilderTest extends TestCase {
         fail();
     }
 
+    public void testSuper() {
+        Object obj = new Object();
+        assertEquals(17 * 37 + (19 * 41 + obj.hashCode()), new HashCodeBuilder(17, 37).appendSuper(
+            new HashCodeBuilder(19, 41).append(obj).toHashCode()
+        ).toHashCode());
+    }
+
     public void testObject() {
         Object obj = null;
         assertEquals(17 * 37, new HashCodeBuilder(17, 37).append(obj).toHashCode());