示例：
public class A { B b = new B(); public A() { System.out.PRint("A"); }}public class B { public B() { System.out.print("B"); }}public class C { public C() { System.out.print("C"); }}public class D extends A { C c = new C(); public D() { System.out.print("D"); }}//测试public static void main(String[] args) { D d = new D();}//结果：BACD新闻热点
疑难解答
