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Different behavior of overriding methods and fields

Tags:

java


I just noticed that overriding methods does behave different than overriding fields. Considering the following snippet:

public class Bar {
  int v =1;

  public void printAll(){
    System.out.println(v);
    printV();
  }

  public void printV(){
    System.out.println("v is " + v);
  }
}

public class Foo extends Bar {
  int v = 4;

  public static void main(String[] args) {
    Foo foo = new Foo();
    foo.printAll();
 }

 public void printV() {
   System.out.println("The value v is  " + v);
 }
}

It result in the output:
1
The value v is 4

So it seems that the method printV in bar is overridden by foo.printV while the field v is not overwritten in bar. Does anyone know a reason for this difference?

Thanks.

like image 602
Malte Avatar asked Jan 15 '23 19:01

Malte


1 Answers

I just noticed that overriding methods does behave different than overriding fields.

There's no such thing as "overriding fields". You can shadow fields, but you can't override them. Fields aren't polymorphic. See section 6.4.1 of the Java Language Specification for more details.

Note that in general, fields should almost always be private anyway, which means you wouldn't be aware of this in the first place.

like image 135
Jon Skeet Avatar answered Jan 18 '23 08:01

Jon Skeet