doTryFinallyForMethod support void return type CtMethod

README.md

@@ -82,9 +82,9 @@
 
 相比[`InheritableThreadLocal`](https://docs.oracle.com/javase/10/docs/api/java/lang/InheritableThreadLocal.html)，添加了
 
-1. `protected`方法`copy`  
+1. `copy`方法  
     用于定制 **任务提交给线程池时** 的`ThreadLocal`值传递到 **任务执行时** 的拷贝行为，缺省传递的是引用。
-1. `protected`方法`beforeExecute`/`afterExecute`  
+1. `protected`的`beforeExecute`/`afterExecute`方法  
     执行任务(`Runnable`/`Callable`)的前/后的生命周期回调，缺省是空操作。
 
 具体使用方式见下面的说明。

src/main/java/com/alibaba/ttl/threadpool/agent/internal/transformlet/impl/TtlForkJoinTransformlet.java

@@ -57,16 +57,16 @@ public class TtlForkJoinTransformlet implements JavassistTransformlet {
         logger.info("add new field " + capturedFieldName + " to class " + className);
 
         final CtMethod doExecMethod = clazz.getDeclaredMethod("doExec", new CtClass[0]);
-        final String doExec_renamed_method_rename = renamedMethodNameByTtl(doExecMethod);
+        final String doExec_renamed_method_name = renamedMethodNameByTtl(doExecMethod);
 
         final String beforeCode = "if (this instanceof " + TtlEnhanced.class.getName() + ") {\n" + // if the class is already TTL enhanced(eg: com.alibaba.ttl.TtlRecursiveTask)
-                "    return " + doExec_renamed_method_rename + "($$);\n" +                         // return directly/do nothing
+                "    return " + doExec_renamed_method_name + "($$);\n" +                           // return directly/do nothing
                 "}\n" +
                 "Object backup = com.alibaba.ttl.TransmittableThreadLocal.Transmitter.replay(" + capturedFieldName + ");";
 
         final String finallyCode = "com.alibaba.ttl.TransmittableThreadLocal.Transmitter.restore(backup);";
 
-        doTryFinallyForMethod(doExecMethod, doExec_renamed_method_rename, beforeCode, finallyCode);
+        doTryFinallyForMethod(doExecMethod, doExec_renamed_method_name, beforeCode, finallyCode);
     }
 
     private void updateConstructorDisableInheritable(@NonNull final CtClass clazz) throws NotFoundException, CannotCompileException {

src/main/java/com/alibaba/ttl/threadpool/agent/internal/transformlet/impl/Utils.java

@@ -68,11 +68,17 @@ public class Utils {
                 & ~Modifier.PROTECTED /* remove protected */
                 | Modifier.PRIVATE /* add private */);
 
+        final String returnOp;
+        if (method.getReturnType() == CtClass.voidType) {
+            returnOp = "";
+        } else {
+            returnOp = "return ";
+        }
         // set new method implementation
         final String code = "{\n" +
                 beforeCode + "\n" +
                 "try {\n" +
-                "    return " + renamedMethodName + "($$);\n" +
+                "    " + returnOp + renamedMethodName + "($$);\n" +
                 "} finally {\n" +
                 "    " + finallyCode + "\n" +
                 "} }";