Exception when access inner class reflectively

Question

Hi Folk, Here is a sample java program. I wonder why the two approaches reslut different stories. Is it a bug or kind of bitter java feature?

And I run the sample upon java 1.5

package test;

public class TestOut{

public static void main(String[] args){

**new TestIn();//it works**

// throw IllegalAccessException**
**Class.forName("test.TestOut$TestIn").newInstance();
}

private static class TestIn{}

}

Answer 1

The class is private, hence the IllegalAccessException - you can use:

Class cls = Class.forName(...);
Constructor c = cls.getDeclaredConstructors()[0];
c.setAccessible(true);
c.newInstance();

For the record, the exception has a message, which is quite descriptive. Next time don't omit such information from the question. (actually, I'm not sure this message exists on Java 1.5, does it?)

Class test.Test can not access a member of class test.TestOut$TestIn with modifiers "private"

The problem lies in the verifyMemberAccess(..) method of sun.reflect.Reflection, and that it doesn't take into account enclosing classes. If a member (constructor) is private, access is denied.

Answer 2

This is Bug ID 4221909:

Synopsys: (reflect) Class.newInstance() throws IllegalAccessErrorException when the class has an inner non-public class
State: 6-Fix Understood, bug
Priority: 4-Low
Submit Date: 19-MAR-1999