update faq.md

site/src/site/sphinx/en/faq.md

@@ -24,7 +24,7 @@ com.sun.tools.attach.AttachNotSupportedException: Unable to open socket file: ta
 
 ##### Can commands such as trace/watch enhance the classes in jdk?
 
-By default, classes beginning with `java.` are filtered out, but they can be turned on:
+By default, classes beginning with `java.` or the classes loaded by the `Bootstrap ClassLoader` are filtered out, but they can be turned on:
 
 ```bash
 options unsafe true
@@ -32,6 +32,7 @@ options unsafe true
 
 See more at [options](options.md)
 
+> To support the jars appended by java.lang.instrument.Instrumentation#appendToBootstrapClassLoaderSearch need to enable unsafe.
 
 ##### How to view the result in `json` format
 
@@ -70,6 +71,14 @@ watch demo.MathGame primeFactors '{params,returnObj,throwExp}' 'params.length >0
 watch demo.MathGame <init> '{params,returnObj,throwExp}' -v
 ```
 
+##### How to watch or trace inner classes?
+
+In the JVM specification the name of inner classes is `OuterClass$InnerClass`.
+
+```bash
+watch OuterClass$InnerClass
+````
+
 ##### Enter Unicode characters
 
 Convert Unicode characters to `\u` representation:

site/src/site/sphinx/faq.md

@@ -23,7 +23,7 @@ com.sun.tools.attach.AttachNotSupportedException: Unable to open socket file: ta
 4. 更多情况参考： [https://github.com/alibaba/arthas/issues/347](https://github.com/alibaba/arthas/issues/347)
 ##### trace/watch等命令能否增强jdk里的类？
 
-默认情况下会过滤掉`java.`开头的类，但可以通过参数开启。
+默认情况下会过滤掉`java.`开头的类和被`BootStrap ClassLoader`加载的类。可以通过参数开启。
 
 ```bash
 options unsafe true
@@ -31,6 +31,8 @@ options unsafe true
 
 更多参考 [options](options.md)
 
+> 通过 java.lang.instrument.Instrumentation#appendToBootstrapClassLoaderSearch append到`Bootstrap ClassLoader`的jar包需要开启unsafe。
+
 ##### 怎么以`json`格式查看结果
 
 ```bash
@@ -69,6 +71,14 @@ watch demo.MathGame primeFactors '{params,returnObj,throwExp}' 'params.length >0
 watch demo.MathGame <init> '{params,returnObj,throwExp}' -v
 ```
 
+##### 怎样watch、trace内部类？
+
+在JVM规范里内部类的格式是`OuterClass$InnerClass`。
+
+```bash
+watch OuterClass$InnerClass
+```
+
 ##### 输入中文/Unicode字符
 
 把中文/Unicode字符转为`\u`表示方法：