Class scope variable vs method scope variable

Question

I know that variable scope is enclosed by a start of block { and an end of block }. If the same variable is declared within the block, then the compile

Answer 1

Because that's the way Java was designed. The language designers could easily have made it so that it was impossible to use the same name for a local variable and an instance variable. They simply chose not to.

Answer 2

This is because int x=0 is not a variable but an instance field. Local variables are allowed to have the same names as fields. To distinguish between a variable and a field with the same name we use this prefix for instance fields or class name for class fields. E.g.

int x = this.x

Answer 3

Here is a good example of java scopes (from OCA java SE-7). Here z(class variable) is initialized inside the method, doStuff2. Class variables can be initialized inside the method but if the same variable is re-declared inside a method, a new local variable is created on the stack instead of the heap.

            public class ScopeTest
            {
            int z;
            public static void main(String[] args){
            ScopeTest myScope = new ScopeTest();
            int z = 6;
            System.out.println(z);
            myScope.doStuff();
            System.out.println(z);
            System.out.println(myScope.z);
            }
            void doStuff() {
            int z = 5;
            doStuff2();
            System.out.println(z);
            }
            void doStuff2()
            {
            z = 4;
            }
            }

The output:

6 
5 
6 
4