java的继承现象

public class q { public static void main(String[] args) { A a = new A(); B b = new B(); a.s = "[AA]"; b.s = "[BB]"; a = b; System.out.println(a.s); System.out.println(b.s); System.out.println(a.getS()); System.out.println(b.getS()); System.out.println("---------"); ((A)b).s = "[AA]"; System.out.println(a.s); System.out.println(b.s); System.out.println(a.getS()); System.out.println(b.getS()); } } class A { String s = "[A]"; String getS() { return s; } } class B extends A { String s = ""; String getS() { return s; } }

输出：

E:/java>java q [A] [BB] [BB] [BB] --------- [AA] [BB] [BB] [BB]