The Java Language Specification, Third Edition

BLOCKS AND STATEMENTS Scope of Local Variable Declarations 14.4.2
including any further declarators to the right in the local variable declaration statement.
The name of a local variable v may not be redeclared as a local variable of the
directly enclosing method, constructor or initializer block within the scope of v,or
a compile-time error occurs. The name of a local variable v may not be redeclared
as an exception parameter of a catch clause in a try statement of the directly
enclosing method, constructor or initializer block within the scope of v, or a compile-time
error occurs. However, a local variable of a method or initializer block
may be shadowed (§6.3.1) anywhere inside a class declaration nested within the
scope of the local variable.
A local variable cannot be referred to using a qualified name (§6.6), only a
simple name.
The example:
class Test {
static int x;
public static void main(String[] args) {
int x = x;
}
}
causes a compile-time error because the initialization of x is within the scope of
the declaration of x as a local variable, and the local x does not yet have a value
and cannot be used.
The following program does compile:
class Test {
static int x;
public static void main(String[] args) {
int x = (x=2)*2;
System.out.println(x);
}
}
because the local variable x is definitely assigned (§16) before it is used. It prints:
4
Here is another example:
class Test {
public static void main(String[] args) {
System.out.print("2+1=");
int two = 2, three = two + 1;
System.out.println(three);
}
}
which compiles correctly and produces the output:
2+1=3
DRAFT
365