...
//通过key存储的集合
private final Map<SelectionKey, Runnable> inputCallbackMap = new HashMap<>();
...
//塞入集合 
if (key == null) {
    try {
        //注册selector得到key
        key = channel.register(selector, registerOps);
        //根据key
        outputCallbackMap.put(key, callback);
    } catch (ClosedChannelException ignore) {
        return null;
    }
}
...
//调用handle，根据SelectionKey获取runnable进行回调
try {
    if (readSelector.select() == 0) {
        waitSelection(inRegInput);
        continue;
    }
    Set<SelectionKey> selectionKeys = readSelector.selectedKeys();
    for (SelectionKey selectionKey : selectionKeys) {
        if (selectionKey.isValid()) {
            handleSelection(selectionKey, SelectionKey.OP_READ, inputCallbackMap, inputHandlePool);
        }
    }
    selectionKeys.clear();//这里clear，把selectionKey都置空的是咋回事？？？
} catch (IOException e) {
    e.printStackTrace();
}

这边clear掉以后，再unRegister的时候，能remove掉对应的runnable么？