The hashCode() method now generates a magic prime instead of 0 for the hash of null values; this reduces collisions.

3 files changed, 9 insertions, 5 deletions

diff --git a/src/core/lombok/core/handlers/HandlerUtil.java b/src/core/lombok/core/handlers/HandlerUtil.java
index 87462921..a9a4be78 100644
--- a/src/core/lombok/core/handlers/HandlerUtil.java
+++ b/src/core/lombok/core/handlers/HandlerUtil.java
@@ -68,6 +68,10 @@ public class HandlerUtil {
 		return 97;
 	}
 	
+	public static int primeForNull() {
+		return 43;
+	}
+	
 	/** Checks if the given name is a valid identifier.
 	 * 
 	 * If it is, this returns {@code true} and does nothing else.
diff --git a/src/core/lombok/eclipse/handlers/HandleEqualsAndHashCode.java b/src/core/lombok/eclipse/handlers/HandleEqualsAndHashCode.java
index 7e2ff513..77fe3a52 100644
--- a/src/core/lombok/eclipse/handlers/HandleEqualsAndHashCode.java
+++ b/src/core/lombok/eclipse/handlers/HandleEqualsAndHashCode.java
@@ -358,7 +358,7 @@ public class HandleEqualsAndHashCode extends EclipseAnnotationHandler<EqualsAndH
 					statements.add(createResultCalculation(source, fieldAccessor));
 				} else /* objects */ {
 					/* final java.lang.Object $fieldName = this.fieldName; */
-					/* $fieldName == null ? 0 : $fieldName.hashCode() */
+					/* $fieldName == null ? NULL_PRIME : $fieldName.hashCode() */
 					statements.add(createLocalDeclaration(source, dollarFieldName, generateQualifiedTypeRef(source, TypeConstants.JAVA_LANG_OBJECT), fieldAccessor));
 					
 					SingleNameReference copy1 = new SingleNameReference(dollarFieldName, p);
@@ -375,8 +375,8 @@ public class HandleEqualsAndHashCode extends EclipseAnnotationHandler<EqualsAndH
 					setGeneratedBy(nullLiteral, source);
 					EqualExpression objIsNull = new EqualExpression(copy2, nullLiteral, OperatorIds.EQUAL_EQUAL);
 					setGeneratedBy(objIsNull, source);
-					IntLiteral int0 = makeIntLiteral("0".toCharArray(), source);
-					ConditionalExpression nullOrHashCode = new ConditionalExpression(objIsNull, int0, hashCodeCall);
+					IntLiteral intMagic = makeIntLiteral(String.valueOf(HandlerUtil.primeForNull()).toCharArray(), source);
+					ConditionalExpression nullOrHashCode = new ConditionalExpression(objIsNull, intMagic, hashCodeCall);
 					nullOrHashCode.sourceStart = pS; nullOrHashCode.sourceEnd = pE;
 					setGeneratedBy(nullOrHashCode, source);
 					statements.add(createResultCalculation(source, nullOrHashCode));
diff --git a/src/core/lombok/javac/handlers/HandleEqualsAndHashCode.java b/src/core/lombok/javac/handlers/HandleEqualsAndHashCode.java
index 1a6f4a8f..c36b0016 100644
--- a/src/core/lombok/javac/handlers/HandleEqualsAndHashCode.java
+++ b/src/core/lombok/javac/handlers/HandleEqualsAndHashCode.java
@@ -307,7 +307,7 @@ public class HandleEqualsAndHashCode extends JavacAnnotationHandler<EqualsAndHas
 				statements.append(createResultCalculation(typeNode, maker.Apply(List.<JCExpression>nil(), hcMethod, List.of(fieldAccessor))));
 			} else /* objects */ {
 				/* final java.lang.Object $fieldName = this.fieldName; */
-				/* $fieldName == null ? 0 : $fieldName.hashCode() */
+				/* $fieldName == null ? NULL_PRIME : $fieldName.hashCode() */
 				
 				Name dollarFieldName = dollar.append(((JCVariableDecl)fieldNode.get()).name);
 				statements.append(maker.VarDef(maker.Modifiers(finalFlag), dollarFieldName, genJavaLangTypeRef(typeNode, "Object"), fieldAccessor));
@@ -315,7 +315,7 @@ public class HandleEqualsAndHashCode extends JavacAnnotationHandler<EqualsAndHas
 				JCExpression hcCall = maker.Apply(List.<JCExpression>nil(), maker.Select(maker.Ident(dollarFieldName), typeNode.toName("hashCode")),
 						List.<JCExpression>nil());
 				JCExpression thisEqualsNull = maker.Binary(CTC_EQUAL, maker.Ident(dollarFieldName), maker.Literal(CTC_BOT, null));
-				statements.append(createResultCalculation(typeNode, maker.Conditional(thisEqualsNull, maker.Literal(0), hcCall)));
+				statements.append(createResultCalculation(typeNode, maker.Conditional(thisEqualsNull, maker.Literal(HandlerUtil.primeForNull()), hcCall)));
 			}
 		}