1 public class cf { 2  3     /** 4      * 實際上這里涉及方法調用的優先問題， 5      * 優先級由高到低依次為：this.show(O)、super.show(O)、this.show((super)O)、super.show((super)O)。 6      */ 7     public static void main(String[] args) { 8  9         A a1 = new A();10         A a2 = new B();11         B b = new B();12         C c = new C();13         D d = new D();14         System.out.PRintln(a1.show(b)); // ① A and A15         System.out.println(a1.show(c)); // ② A and A16         System.out.println(a1.show(d)); // ③ A and D17         System.out.println(a2.show(b)); // ④ B and A18         System.out.println(a2.show(c)); // ⑤ B and A19         System.out.println(a2.show(d)); // ⑥ A and D20         System.out.println(b.show(b)); // ⑦ B and B21         System.out.println(b.show(c)); // ⑧ B and B22         System.out.println(b.show(d)); // A and D23     }24 }25 26 class A {27     public String show(D obj) {28         return ("A and D");29     }30 31     public String show(A obj) {32         return ("A and A");33     }34 }35 36 class B extends A {37     public String show(B obj) {38         return ("B and B");39     }40 41     public String show(A obj) {42         return ("B and A");43     }44 }45 46 class C extends B {47 }48 49 class D extends B {50 }

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