why `java.lang.SecurityException: Prohibited package name: java` is required?

Question

I created a class \"String\" and placed that in package \"java\" [ actually i wanted to create java.lang to see which class is loaded by classLoader as

Answer 1

From the ClassLoader.defineClass(..) javadoc:

...The specified class name cannot begin with " java. ", since all classes in the " java.* packages can only be defined by the bootstrap class loader

and

Throws: ... SecurityException - If an attempt is made to add this class to a package that contains classes that were signed by a different set of certificates than this class, or if the class name begins with " java. ".