Same field name in the superclass and subclass

Hello

I would like to know what the effect is when you have two fields with the same name in a superclass and subclass. Something along the lines of:
class Base
{
   int x = 0;
}

class Derived extends Base
{
   int x = 1;
}
If I store a reference to an object derived in a variable called base Base reference and I do base.x I get 0.
If I store the reference in a variable of reference Derived called der and I do der.x I get 1.
Are there in fact two fields with the name of x in the case of Derived?

Thank you.

Published by: 953012 on March 24, 2013 16:32

Published by: 953012 on March 24, 2013 16:33

And once more, you need to see the Java language specification. It answers questions such as yours and examples. See the examples.
http://docs.Oracle.com/javase/specs/JLS/SE7/HTML/JLS-8.html#d5e10238
>
Example 8.3.1.1 - 3. Hiding of Instance Variables
. . .

because the declaration of x in the class Test hides the definition of x in the Point class, so class Test does not inherit the field x from its superclass Point. It should be noted, however, that if the field x of class Point is not inherited from the Test class, it is nevertheless implemented by instances of the Test class. In other words, each instance of class Test contains two fields, one of type int and one of type double. The two fields are named x, but in the declaration of class Test, the name of simple x always refers to the field declared in the test Code class in the instance of Test methods may refer to the instance variable x of class Point as super.x.

Code that uses a field access x field access expression will access the field named x in the class indicated by the type of the expression to reference. Thus, the expression sample.x accesses a value of type double, the instance reported in the Test class, variable type variable sample is a Test, but the expression ((Point) sample) .x accesses an int value, the instance variable declared in class Point, because of the cast to type Point.
>
Have you seen this part? "each instance of class Test contains two fields, one of type int and one of type double.

Tags: Java

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