refact and remove unused method

agent/src/main/java/com/alibaba/testable/agent/handler/BaseClassHandler.java

@@ -22,6 +22,10 @@ abstract public class BaseClassHandler implements Opcodes {
         return cw.toByteArray();
     }
 
+    /**
+     * Transform class byte code
+     * @param cn original class node
+     */
     abstract protected void transform(ClassNode cn);
 
 }

agent/src/main/java/com/alibaba/testable/agent/model/MethodInfo.java

@@ -1,30 +1,18 @@
 package com.alibaba.testable.agent.model;
 
-import java.util.Collection;
-import java.util.HashSet;
-import java.util.Set;
-
 /**
  * @author flin
  */
 public class MethodInfo {
 
-    private String name;
-    private String desc;
+    private final String name;
+    private final String desc;
 
     public MethodInfo(String name, String desc) {
         this.name = name;
         this.desc = desc;
     }
 
-    public static Set<String> descSet(Collection<MethodInfo> methodInfos) {
-        Set<String> set = new HashSet<String>();
-        for (MethodInfo m : methodInfos) {
-            set.add(m.desc);
-        }
-        return set;
-    }
-
     public String getName() {
         return name;
     }

agent/src/main/java/com/alibaba/testable/agent/transformer/TestableClassTransformer.java

@@ -19,7 +19,7 @@ import java.util.Set;
  */
 public class TestableClassTransformer implements ClassFileTransformer {
 
-    private static final Set<String> loadedClassNames = new HashSet<String>();
+    private final Set<String> loadedClassNames = new HashSet<String>();
 
     public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined,
                             ProtectionDomain protectionDomain, byte[] classFileBuffer) {

core/src/main/java/com/alibaba/testable/core/accessor/PrivateAccessor.java

@@ -33,14 +33,17 @@ public class PrivateAccessor {
 
     public static <T> T invoke(Object ref, String method, Object... args) {
         try {
-            Class[] cls = TypeUtil.getClassesFromObjects(args);
+            Class<?>[] cls = TypeUtil.getClassesFromObjects(args);
             Method declaredMethod = TypeUtil.getMethodByNameAndParameterTypes(ref.getClass().getDeclaredMethods(), method, cls);
-            declaredMethod.setAccessible(true);
-            return (T)declaredMethod.invoke(ref, args);
+            if (declaredMethod != null) {
+                declaredMethod.setAccessible(true);
+                return (T)declaredMethod.invoke(ref, args);
+            }
         } catch (Exception e) {
             e.printStackTrace();
             return null;
         }
+        return null;
     }
 
 }

core/src/main/java/com/alibaba/testable/core/translator/BaseTranslator.java

@@ -17,9 +17,14 @@ public abstract class BaseTranslator extends TreeTranslator {
             }
             return List.from(es);
         }
-        return null;
+        return List.nil();
     }
 
+    /**
+     * Exchange private method invoke with private accessor
+     * @param expr original expression
+     * @return exchanged expression
+     */
     protected abstract JCExpression checkAndExchange(JCExpression expr);
 
 }