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

abstract class emptyAb {}

题目二

abstract class Base{
    abstract public void myfunc();
}

public class Abs extends Base{
    public static void main(String argv[]){
        Abs a = new Abs();
        a.amethod();
    }

    public void amethod(){
        System.out.println("A method");
    }
}

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