Java invocation by subclass how the parent class has been overridden method

class A {
void a () {
System.out.println ("parent'a ()");
}
}

class AA extends A {
void a () {
System.out.println ("child'a ()");
}
}

public static void main (String [] agrs) {
AA aa = new AA ();
aa.a ();
A a = (A) aa;
a.a ();
}

Both print out the results are the same, how to call a method in A , A and AA without changing the way the case .
------ Solution ---------------------------------------- ----
A a = (A) aa;
you this wording is actually polymorphic writing, running, or AA, because you override the parent class method , want to call the parent class method, you just go directly to the new parent class A a = new A ();
------ Solution -------------------------------- ------------
AA aa = new AA ();

Since you construct the AA, A then stop thinking about it.
------ Solution ---------------------------------------- ----

  class AA extends A{
    void a(){
    System.out.println("child'a()");
    }
    void sa(){
    new A().a();
  }
  }
  
  

a.sa ();
------ Solution ---------------------------- ----------------
want to call that method a, there must be an instance of that object . A a = (A) aa; wrote , that the real object or AA, so it will call the AA with that method .
------ Solution ---------------------------------------- ----
you upcast when, in fact invoked method is overridden by subclasses way , that is, polymorphism, you can new subclass object , if the super. methods ( ) , it can Kazakhstan .
------ Solution ---------------------------------------- ----
reflection ?
------ Solution ---------------------------------------- ----
subclass call the parent class is overridden method, using super. overridden method ( ) can be !
------ Solution ---------------------------------------- ----


supports 13 floor.
------ Solution ---------------------------------------- ----
right, with a super positive solution
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in fact, I just want to know how to access through the only class has been overridden method !
His type is changed or why the point is that AA does not point A.
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that the wording and
A a = new AA (); wrote no difference , polymorphism
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static method

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how reflection , just read a little , how to get A reflection of this class too !
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this is a subclass call the parent class , AA a = new A (), then call no problem
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will complain , and sub-class can not be explicitly converted to the parent class
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13 F, positive solution , this is a java and c + + is a very important distinction , in c + + , you can move upward through such type of operation to achieve the call the parent class act , and in Java, no matter what its type conversion , and its type is actually the same.

cite a simple example , C + + in

  class A {
  public:
    void print(){
      cout<<"Class A"<<endl;
    }
  };
  
  class B: public A{
  public:
    void print(){
      cout<<"Class B"<<endl;
    }
  };
  
  int main(){
      B b;
      A a = (A)b;
      a.print();
      A *aa = new B();
      aa->print();
      cout<<typeid(a).name()<<endl;
      system("PAUSE");
      return 0;
  }
  

the output is

Class A
Class A
1A

DESCRIPTION type promotion has become the object type b A type. Therefore, the behavior of call A , the A Perceptual behavior.

But this is indeed the contrary in java , see the following code:

  class Base{
  	public String getFields(){
  		return "Base";
  	}
  }
  
  class Agg extends Base{
  	public String getFields(){
  		return "AGG";
  	}
  	public String getSuperFiedls(){
  		return super.getFields();
  	}
  }
  

execute this code
Agg agg = new Agg ();
Base base = new Agg ();
if (base instanceof Agg)
System.out.println ("Class Agg");
else
System.out.println ("Class Base");
System.out.println (base.getFields ());
System.out.println (agg.getSuperFiedls ());

Results

Class Agg
AGG
Base

this can be , regardless of how the Java objects for type promotion , retains its original type.

Today is also encountered this problem well summed up what I hope this can help people to see .
------ For reference only -------------------------------------- -
class AA extends A {
void a () {
super.a ();
System.out.println ("child'a ()");
}
}