Why is it declared final when using local variables in an anonymous class?

When there are two threads inside a method that share internal class objects, the local variables of this method can be accessed,

It becomes a critical resource, causing the program to be unstable, so it must be final.

Anyway, Java is not allowing you to change the local variables of the method inside the local inner class.

public class MyBase {

Public anoclass func (final int i) { 
return new Anoclass () { 
int j=i; 
{ 
System.out.println ("Anonymous Inner class"); 
} 
public void Func () { 
System.out.println ("Inner anoclass"); 
} 
}; 
} 
/** 
* @param args 
*/ 
public static void Main (string[] args) { 
MyBase MyBase = new MyBase (); 
Anoclass Anoclass = Mybase.func (5); 
Anoclass.func (); 
}

}

Class anoclass{
public void Func () {
System.out.println ("Anoclass.");  
} 
}

Why is it declared final when using local variables in an anonymous class?