问下 inner class 里想写 static nested class 作为工具类的时候该怎么办

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Inner class 里不能写 static nested class，可是有些场景感觉这么封装最合适 Orz

public class Outer {
    class Inner {
    	// static class Helper {} // error
    }
}

举个栗子

public class BTree {
	class Node {
		/*static*/ class Pair {
			final int k;
			final double v;
		}
		// blabla..
	}
	// blabla..
}

5 replies • 2019-04-09 23:40:58 +08:00

karia

Apr 2, 2019

可能应该把 Inner 写成 package-private 的顶级类了

karia

Apr 2, 2019

但是 Inner 要访问 Outer 的 field 的时候非要这么拆就影响內聚

lzdhlsc

Apr 2, 2019

inner static class 如何? public static class Node...

zealot0630

Apr 2, 2019 via Android

static is evil。static 破坏了语言的 lexical scope，outer class 的成员明显在你的 scope 里面，你却无法访问。参考 scala 是怎么去掉 static 关键字的，一方面用 Singleton 取代了，另一方面，强制你必须放外面去

ChanKc

Apr 9, 2019

@zealot0630 If you declare a member class that does not require access to an enclosing instance, always put the static modifier in its declaration, making it a static rather than a nonstatic member class.

来自 Effective Java 3rd Edition Item 24