构造函数并实现继承组合等

怎么写啊这个，搞不懂，

public class A{
  public A(){
        System.out.println("A"):
  }
}

public class B1{
  public B1(){
        System.out.println("B1"):
  }
}

public class B2{
  public B2(){
        System.out.println("B2"):
  }
}

public class B extends A{
  B1 b1;
  B2 b2;
  public B(){
        System.out.println("B"):
        b1 =  new B1();
        b2 =  new B2();
  }
}

public class C extends B{
  public C(){
        System.out.println("C"):
  }
}

public class Test{
  public static void main(String[] args){
        C c = new C();
        System.out.println("Test"):
  }
}