diff --git a/src/main/java/il/ac/technion/cs/fling/adapters/JavaASTVisitorAdapter.java b/src/main/java/il/ac/technion/cs/fling/adapters/JavaASTVisitorAdapter.java
index 075619f9..f25c6394 100644
--- a/src/main/java/il/ac/technion/cs/fling/adapters/JavaASTVisitorAdapter.java
+++ b/src/main/java/il/ac/technion/cs/fling/adapters/JavaASTVisitorAdapter.java
@@ -1,117 +1,117 @@
 package il.ac.technion.cs.fling.adapters;
-import static java.util.stream.Collectors.joining;
-import java.util.LinkedHashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.Objects;
+
 import il.ac.technion.cs.fling.internal.compiler.Namer;
-import il.ac.technion.cs.fling.internal.compiler.ast.nodes.ASTCompilationUnitNode;
-import il.ac.technion.cs.fling.internal.compiler.ast.nodes.AbstractClassNode;
-import il.ac.technion.cs.fling.internal.compiler.ast.nodes.ClassNode;
-import il.ac.technion.cs.fling.internal.compiler.ast.nodes.ConcreteClassNode;
-import il.ac.technion.cs.fling.internal.compiler.ast.nodes.FieldNode;
+import il.ac.technion.cs.fling.internal.compiler.ast.nodes.*;
 import il.ac.technion.cs.fling.internal.grammar.rules.Variable;
 import il.ac.technion.cs.fling.internal.grammar.sententials.quantifiers.JavaCompatibleQuantifier;
 import il.ac.technion.cs.fling.namers.NaiveNamer;
-/** Java adapter printing AST visitor class given AST type definitions.
+
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+
+import static java.lang.String.format;
+import static java.util.stream.Collectors.joining;
+
+/**
+ * Java adapter printing AST visitor class given AST type definitions.
  *
- * @author Ori Roth */
-@SuppressWarnings("static-method") public class JavaASTVisitorAdapter {
+ * @author Ori Roth
+ */
+@SuppressWarnings("static-method")
+public class JavaASTVisitorAdapter {
   private final String astClassName;
   private final Namer namer;
   private final String packageName;
+
   public JavaASTVisitorAdapter(final String packageName, final String astClassName, final Namer namer) {
     this.packageName = packageName;
     this.astClassName = astClassName;
     this.namer = namer;
   }
+
   public String printASTVisitorClass(final ASTCompilationUnitNode compilationUnit) {
-    return String.format("public static class %s{%s%s}", //
-        VISITOR_CLASS_NAME, //
-        compilationUnit.classes.stream() //
-            .map(this::printVisitMethod) //
-            .collect(joining()), //
-        compilationUnit.classes.stream() //
-            .filter(ClassNode::isConcrete) //
-            .map(ClassNode::asConcrete) //
-            .map(this::printWhileVisitingMethod) //
-            .collect(joining()));
+    return format("public interface %s{%s}", //
+            VISITOR_CLASS_NAME, //
+            compilationUnit.classes.stream() //
+                    .map(this::printVisitMethod) //
+                    .collect(joining()));
   }
+
   public String printVisitMethod(final AbstractClassNode clazz) {
     final Variable source = clazz.source;
     final String parameterName = getNodeParameterName(source);
-    return String.format("public final void visit(%s %s){%s}", //
-        getASTVariableClassName(source), //
-        parameterName, //
-        printVisitMethodBody(clazz, parameterName));
+    return format("default void visit(%s %s){%s}", //
+            getASTVariableClassName(source), //
+            parameterName, //
+            printVisitMethodBody(clazz, parameterName));
   }
+
   public String printVisitMethod(final ClassNode clazz) {
     return clazz.isAbstract() ? //
-        printVisitMethod(clazz.asAbstract()) : //
-        printVisitMethod(clazz.asConcrete());
+            printVisitMethod(clazz.asAbstract()) : //
+            printVisitMethod(clazz.asConcrete());
   }
+
   public String printVisitMethod(final ConcreteClassNode clazz) {
     final Variable source = clazz.source;
     final String parameterName = getNodeParameterName(source);
-    return String.format("public final void visit(%s %s){%s}", //
-        getASTVariableClassName(source), //
-        parameterName, //
-        printVisitMethodBody(clazz, parameterName));
-  }
-  public String printWhileVisitingMethod(final ConcreteClassNode clazz) {
-    final Variable source = clazz.source;
-    final String parameterName = getNodeParameterName(source);
-    return String.format("public void whileVisiting(%s %s)throws %s{}", //
-        getASTVariableClassName(source), //
-        parameterName, //
-        Exception.class.getCanonicalName());
+    return format("default void visit(%s %s){%s}", //
+            getASTVariableClassName(source), //
+            parameterName, //
+            printVisitMethodBody(clazz, parameterName));
   }
+
   private String getASTVariableClassName(final Variable variable) {
-    return String.format("%s.%s.%s", //
-        packageName, //
-        astClassName, //
-        namer.getASTClassName(variable));
+    return format("%s.%s.%s", //
+            packageName, //
+            astClassName, //
+            namer.getASTClassName(variable));
   }
+
   private String getNodeParameterName(final Variable variable) {
     return NaiveNamer.lowerCamelCase(variable.name());
   }
+
   private String printVisitMethodBody(final AbstractClassNode clazz, final String parameterName) {
     return clazz.children.stream() //
-        .map(child -> String.format("if(%s instanceof %s)%s", //
-            parameterName, //
-            getASTVariableClassName(child.source), //
-            variableVisitingStatement(child.source, parameterName))) //
-        .collect(joining("else "));
+            .map(child -> format("if(%s instanceof %s)%s", //
+                    parameterName, //
+                    getASTVariableClassName(child.source), //
+                    variableVisitingStatement(child.source, parameterName))) //
+            .collect(joining("else "));
   }
+
   private String printVisitMethodBody(final ConcreteClassNode clazz, final String parameterName) {
     final StringBuilder $ = new StringBuilder();
     final Map<String, Integer> usedNames = new LinkedHashMap<>();
-    $.append(String.format("try{this.whileVisiting(%s);}catch(%s __){__.printStackTrace();}", //
-        parameterName, //
-        Exception.class.getCanonicalName()));
     clazz.fields.stream() //
-        .map(FieldNode::source) //
-        .forEach(source -> {
-          assert !source.isQuantifier() || source.getClass()
-              .isAnnotationPresent(JavaCompatibleQuantifier.class) : "BNF uses a non-Java-compatible notation";
-        });
+            .map(FieldNode::source) //
+            .forEach(source -> {
+              assert !source.isQuantifier() || source.getClass()
+                      .isAnnotationPresent(JavaCompatibleQuantifier.class) : "BNF uses a non-Java-compatible notation";
+            });
     clazz.fields.stream() //
-        .map(FieldNode::getInferredFieldFragments) //
-        .flatMap(List::stream) //
-        .map(field -> field.visitingStatement(//
-            this::variableVisitingStatement, //
-            String.format("%s.%s", //
-                parameterName, //
-                field.parameterName), //
-            () -> NaiveNamer.getNameFromBase("_x_", usedNames)))
-        .filter(Objects::nonNull) //
-        .forEach($::append);
+            .map(FieldNode::getInferredFieldFragments) //
+            .flatMap(List::stream) //
+            .map(field -> field.visitingStatement(//
+                    this::variableVisitingStatement, //
+                    format("%s.%s", //
+                            parameterName, //
+                            field.parameterName), //
+                    () -> NaiveNamer.getNameFromBase("_x_", usedNames)))
+            .filter(Objects::nonNull) //
+            .forEach($::append);
     return $.toString();
   }
+
   private String variableVisitingStatement(final Variable variable, final String access) {
-    return String.format("{visit((%s)%s);}", //
-        getASTVariableClassName(variable), //
-        access);
+    return format("{visit((%s)%s);}", //
+            getASTVariableClassName(variable), //
+            access);
   }
+
   private static final String VISITOR_CLASS_NAME = "Visitor";
+
 }
diff --git a/src/main/java/il/ac/technion/cs/fling/internal/grammar/types/ClassParameter.java b/src/main/java/il/ac/technion/cs/fling/internal/grammar/types/ClassParameter.java
index 409f3010..f4fa42da 100644
--- a/src/main/java/il/ac/technion/cs/fling/internal/grammar/types/ClassParameter.java
+++ b/src/main/java/il/ac/technion/cs/fling/internal/grammar/types/ClassParameter.java
@@ -1,6 +1,8 @@
 package il.ac.technion.cs.fling.internal.grammar.types;
+
+import static il.ac.technion.cs.fling.namers.NaiveNamer.lowerCamelCase;
+import static il.ac.technion.cs.fling.namers.NaiveNamer.unreservedName;
 import static java.util.Objects.requireNonNull;
-import il.ac.technion.cs.fling.namers.NaiveNamer;
 // TODO allow primitive types.
 public class ClassParameter implements StringTypeParameter {
   public final Class<?> parameterClass;
@@ -11,7 +13,9 @@ public ClassParameter(final Class<?> parameterClass) {
     return parameterClass.getCanonicalName();
   }
   @Override public String baseParameterName() {
-    return unPrimitiveTypeSimple(NaiveNamer.lowerCamelCase(parameterClass.getSimpleName()));
+    if (parameterClass.isPrimitive())
+      return parameterClass.getSimpleName().substring(0, 1);
+    return unreservedName(lowerCamelCase(parameterClass.getSimpleName()));
   }
   @Override public int hashCode() {
     return parameterClass.hashCode();
@@ -39,16 +43,4 @@ public static String unPrimitiveType(final String typeName) {
                                     void.class.getName().equals(typeName) ? Void.class.getCanonicalName() : //
                                         typeName;
   }
-  public static String unPrimitiveTypeSimple(final String typeName) {
-    return byte.class.getName().equals(typeName) ? "b" : //
-        short.class.getName().equals(typeName) ? "s" : //
-            int.class.getName().equals(typeName) ? "i" : //
-                long.class.getName().equals(typeName) ? "l" : //
-                    float.class.getName().equals(typeName) ? "f" : //
-                        double.class.getName().equals(typeName) ? "d" : //
-                            boolean.class.getName().equals(typeName) ? "b" : //
-                                char.class.getName().equals(typeName) ? "c" : //
-                                    void.class.getName().equals(typeName) ? "v" : //
-                                        typeName;
-  }
 }
diff --git a/src/main/java/il/ac/technion/cs/fling/namers/NaiveNamer.java b/src/main/java/il/ac/technion/cs/fling/namers/NaiveNamer.java
index a85b3b76..e33e438c 100644
--- a/src/main/java/il/ac/technion/cs/fling/namers/NaiveNamer.java
+++ b/src/main/java/il/ac/technion/cs/fling/namers/NaiveNamer.java
@@ -23,6 +23,9 @@
 import il.ac.technion.cs.fling.internal.grammar.rules.Component;
 import il.ac.technion.cs.fling.internal.grammar.rules.Constants;
 import il.ac.technion.cs.fling.internal.grammar.rules.Variable;
+
+import javax.lang.model.SourceVersion;
+
 public class NaiveNamer implements Namer {
   private final Map<Variable, Integer> astChildrenCounter = new HashMap<>();
   private final Map<Component, Integer> notationsChildrenCounter = new HashMap<>();
@@ -168,6 +171,11 @@ public static String getNameFromBase(final String baseName, final Map<String, In
     final int position = usedNames.put(baseName, usedNames.get(baseName) + 1);
     return baseName + position;
   }
+  public static String unreservedName(final String name) {
+    if (!SourceVersion.isKeyword(name))
+      return name;
+    return unreservedName(name + "_");
+  }
   @Override public String headVariableClassName(final Variable variable) {
     return variable.name();
   }