Names - The Java Language Specification - page 131

parameter of a catch clause in a try statement of the directly enclosing method or initializer
block.
The translation of a try -with-resources statement implies the rule above.
Despite the above rules against redeclaration of variables, the rules of shadowing
(§ 6.4.1 ) allow redeclaration in certain nested class declarations (i.e. local classes
(§ 14.3 ) and anonymous classes (§ 15.9 ) ) as follows:
• A formal parameter of a method or constructor may be shadowed anywhere
inside a class declaration nested within that method or constructor.
• A local variable of a method, constructor, or initializer may be shadowed
anywhere inside a class declaration nested within the scope of the local vari-
able.
• A local class declaration may be shadowed anywhere inside a class declara-
tion nested within the local class declaration's scope.
• An exception parameter may be shadowed anywhere inside a class declara-
tion nested within the Block of the catch clause.
• A variable declared in a ResourceSpecification may be shadowed anywhere
inside a class declaration nested within the try Block .
Example 6.4-1. Attempted Shadowing Of A Local Variable
Because a declaration of an identifier as a local variable of a method, constructor, or
initializer block must not appear within the scope of a parameter or local variable of
the same name, a compile-time error occurs for the following program:
Click here to view code image
class Test1 {
public static void main(String[] args) {
int i;
for (int i = 0; i < 10; i++)
System.out.println(i);
}
}
This restriction helps to detect some otherwise very obscure bugs. A similar restric-
tion on shadowing of members by local variables was judged impractical, because the
addition of a member in a superclass could cause subclasses to have to rename loc-
al variables. Related considerations make restrictions on shadowing of local variables