ניתוח היררכיית ירושה ופולימורפיזם

1public class A
2{
3    protected int x;
4
5    public A()
6    {
7        this.x = 9;
8        System.out.println("A. x =  " + this.x);
9    }
10    public A(int x)
11    {
12        this.x = x;
13        System.out.println("A. x =  " + this.x);
14    }
15    public int getX() { return this.x; }
16    public int foo() { return this.x; }
17}
18
19public class B extends A
20{
21    public B() { super(); }
22    public B(int x) { super(x); }
23    public int foo() { return this.x + 1; }
24}
25
26public class C extends B
27{
28    public C() { super(); }
29    public C(int x) { super(x); }
30    public int foo() { return this.x + 2; }
31    public int bar() { return this.x; }
32}
33
34public class D extends C
35{
36    public D()
37    {
38        super();
39        this.x++;
40        System.out.println("D. x = " + this.x);
41    }
42    public D(int x)
43    {
44        super(x);
45        System.out.println("D. x = " + this.x);
46    }
47    public D(int x, int y)
48    {
49        super();
50        this.x = this.x + x + y;
51        System.out.println("D. x = " + this.x);
52    }
53    public int foo() { return this.x - 1; }
54}
55
56public class E extends C
57{
58    public E() { super(); }
59    public int bar() { return this.x + 1; }
60}