abstract 相关问题

题目一

什么是抽象类

  1. A class with no methods
  2. A class with no concrete subclasses
  3. A class with at least one undefiend message
  4. None of above

答案是 4 我们是可以定义一个抽象空类的

  1. abstract class emptyAb {}

题目二

  1. abstract class Base{
  2.     abstract public void myfunc();
  3. }
  5. public class Abs extends Base{
  6.     public static void main(String argv[]){
  7.         Abs a = new Abs();
  8.         a.amethod();
  9.     }
  11.     public void amethod(){
  12.         System.out.println("A method");
  13.     }
  14. }

运行的结果

  1. 输出 A method
  2. The code will compile but complain at run time
  3. The compiler will complain errors in Abs class

答案是 3