Hash codes of key classes are now cached lazily.

Slightly changed the algorithm according the recommendations
in "Effective Java" by Joshua Bloch.

src/helma/objectmodel/db/DbKey.java

@@ -21,6 +21,9 @@ public final class DbKey implements Key, Serializable {
     // the id that defines this key's object within the above storage space
     private final String id;
 
+    // lazily initialized hashcode
+    private transient int hashcode = 0;
+
     /**
      * make a key for a persistent Object, describing its datasource and id.
      */
@@ -44,7 +47,12 @@ public final class DbKey implements Key, Serializable {
     }
 
     public int hashCode () {
-	return storageName == null ? id.hashCode () : storageName.hashCode() + id.hashCode ();
+	if (hashcode == 0) {
+	    hashcode =  storageName == null ?
+		17 + 37*id.hashCode () :
+		17 + 37*storageName.hashCode() + +37*id.hashCode ();
+	}
+	return hashcode;
     }
 
     public Key getParentKey () {

src/helma/objectmodel/db/SyntheticKey.java

@@ -16,6 +16,9 @@ public final class SyntheticKey implements Key, Serializable {
     private final Key parentKey;
     private final String name;
 
+    // lazily initialized hashcode
+    private transient int hashcode = 0;
+
 
     /**
      * make a key for a persistent Object, describing its datasource and id.
@@ -39,7 +42,9 @@ public final class SyntheticKey implements Key, Serializable {
     }
 
     public int hashCode () {
-	return name.hashCode () + parentKey.hashCode ();
+	if (hashcode == 0)
+	    hashcode = 17 + 37*name.hashCode () + 37*parentKey.hashCode ();
+	return hashcode;
     }