How to Create Instance Variable and Class Variable of the Same Name

Why have a class with both a class variable and an instance variable of the same name?

In Python that can be used for defaults.... for example:

class Foo:
    x = 1

a = Foo()
b = Foo()
print(a.x, b.x) # --> 1 1
a.x = 2
print(a.x, b.x) # --> 2 1

Instance variable in derived class has the same name with private instance variable of superclass?

Yes it is possible to declare such a variable, because the variable in the super class is private it cannot be seen in the child class and so there is no conflict.

But note that this is not the same as 'overriding', where an externally visible member is hidden by one with the same name in a child class.

How to keep the name of the instance variable same as that of constructor parameter?

I think this is what you want:

class ms {
    int[] a;

    ms(int[] a) {
        this.a = a;
    }
}

Local variable and instance variable has the same name

The code, as shown, is wrong. The intent here is to assign the value of local variable val to the instance variable val. However, without a qualifier, this code just reassigns the local variable to itself. You’ll see it if you add a final to the constructor parameter.
What you want is this.val = val. It’s common practice to name both the same for legibility, but qualify the instance variable with this.
You also want a basic Java book.

Referring to instance variable with same name as a local variable in a constructor?

There is no class variable in your code.

If you want a class variable, use static int a. Of course, you won't be able to refer to a class variable using this.a: that only works with instance variables.

And, of course, you can't have a class variable and an instance variable with the same name.

If you override the class variable with a local variable, (bad idea - don't do that - most IDEs will warn you) then can refer to the class variable with Foobar.a

java instance variable and method having same name

Yes it's fine, mainly because, syntactically , they're used differently.

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