为什么使用方法本地抽象内部类

问题描述

可以与方法本地内部类一起使用的合法修饰符之一是abstract。

One of the legal modifiers you can use with method local inner classes is abstract.

例如：

public class Outer {
    public void method(){
        abstract class Inner{
        }
    }
}

您是否有实际使用过的情况？

Is there any situation where you would actually use this?

你必须知道这个SCJP考试。

You have to know this for the SCJP exam.

推荐答案

原始问题中的一些无效假设。某些东西是合法/有效的Java并不意味着它是您需要使用或需要知道的东西。

The are some invalid assumptions in the original question. That something is legal/valid Java doesn't mean that it is something that you need to use, or need to know.

我不记得SCJP包含奇怪的案例问题。

I can't recall that the SCJP contains odd corner case questions.

我试图提出我会使用在方法中声明的抽象类的情况，但是一切看起来很奇怪，并且设计糟糕。
这是一个我想出的代码示例（仍然是糟糕的代码设计恕我直言）

I tried to come up with a case where I would have used an abstract class declared in a method, but everything looks very odd, and reeks of bad design.Here's however a code example that I came up with (still bad code design IMHO)

public class BatchExecutor {

    public static enum ResultNotification {
        JMS,
        MAIL
    };

    public Runnable createRunnable(ResultNotification type) {
        abstract class Prototype implements Runnable {
            public void run() {
                performBusinessLogic();
                publishResult();
            }

            abstract void publishResult();
        }

        switch (type) {
            case JMS: {
                return new Prototype() {
                    void publishResult() {
                        //Post result to JMS
                    }
                };
            }
            case MAIL: {
                return new Prototype() {
                    void publishResult() {
                        //Post result to MAIL
                    }
                };
            }
        }
        return null;
    }

    private void performBusinessLogic() {
        //Some business logic
    }

}

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