由bootstrapclassloader加载类(Class loading by bootstrapclassloader)

由bootstrapclassloader加载类(Class loading by bootstrapclassloader)

这是我在采访中被问到的：

如果将一个新方法添加到String类并编译并放入rt.jar，那么将引导类加载器加载吗？

我回答说它不会被装载，但不知道为什么。

请帮助我正确回答和解释。

Here is what I was asked in interview:

If a new method is added to String class and compiled and put in rt.jar, then will bootstrap class loader load it?

I answered that it will not get loaded but could not tell why.

Please help me with correct answer and explanation of that.

最满意答案

它将被加载。

而且不仅如此：它甚至不需要在rt.jar ，如果你将一个jar文件添加到boot-classpath（参见-Xbootclasspath/p:path ），那么你甚至可以从其他jar加载java.lang.*类文件。

这当然是一种违反JVM安全性的方法，但是你需要非常深入的访问（对rt.jar写访问或访问JVM的命令行参数），当你有这些访问时，你可以做一个不仅仅是替换String.toString() 。

It will be loaded.

And not just that: it need not even be in rt.jar, if you prepend a jar file to the boot-classpath (see -Xbootclasspath/p:path), then you can even load java.lang.* classes from other jar files.

This of course is a way to violate the security of the JVM, but you need pretty deep access (either write-access to rt.jar or access to the command line parameters of the JVM) and when you have those, you can do a lot more than just replace String.toString().