Marvin Soliven

yen hoang wrote:Pleaon explain for me why the assign a certain value to a variable in instance initialization block is ok but increment ( or st like that) is not
public class A { { x=8; // it's ok y++;// compile error } int x,y; publlic A() { System.out.println("x= " +x +" y=" +y); } public static void main(String[] arg) { A a= new A(); } }

JLS (§8.3.2.3) has this to say :

The declaration of a member needs to appear before it is used only if the member is an instance (respectively static) field of a class or interface C and all of the following conditions hold:

1. The usage occurs in an instance (respectively static) variable initializer of C or in an instance (respectively static) initializer of C.

2. The usage is not on the left hand side of an assignment.

3. C is the innermost class or interface enclosing the usage.

By incrementing (y++) which is equivalent to (y = y+1) , you implicitly used y at the right side of an assignment. Just IMHO though :-)

Interestingly, if you change y to static int in your declaration, the compiler will not complain anymore See JLS (§8.3.2.2 )

Ruben Soto wrote:Yes, there is no overriding.

and if we comment out the printMe() method from the Inner class, we can see that private methods cannot even be inherited, i.e., calling inn.printMe() instead of inn.testMe() in the main() method, will generate a compile error.

hence, there will be nothing to override