What is the scope of a java variable in a block?

Question

I know that in C ++ variables there is a block area, for example, the following code works in C ++

void foo(){
    int a = 0;
    for(int i = 0; i < 10; ++i){
        int a = 1; //re-define a here.
    }

}

but this fragment does not work in java, it says "duplicate local variable a", does this mean that java variables do not have a BLOCK scope?

Answer 1

java variables have a block scope, but if you notice that int a is already defined in scope

  { 
     int a = 0;
      {
       {
        } 
      }




   }

all undermining are in the area of ​​the topmost braces. Therefore, you get a duplicate variable error.

Answer 2

. , . Java .

Answer 3

Section §14.4.2 :

(§14.2) , , (§14.4) .

v , v .

Answer 4

The previous answers already indicated the reason, but I just want to show that this is still allowed:

void foo(){
    for(int i = 0; i < 10; ++i){
        int a = 1;
    }
    int a = 0;
}

In this case, the ainside does not hide the external a, therefore it is valid.

And IMHO should also be like this in C ++, this is less confusing and prevents accidental declaration of a variable with the same name.

Answer 5

It does, but it is nested, so the "a" you defined in foo () is available in all blocks inside foo.

Here is an example of what you are looking for:

void foo(){
    {
        int a = 0;
        // Do something with a
    }
    for(int i = 0; i < 10; ++i){
        int a = 1; //define a here.
    }
}