My ViewModel observer returns an ArrayList<ContactObject> (contactsList) which I want to filter and sort before setting RecyclerView wit,sorting,kotlin,arraylist,classcastexception"/>

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My ViewModel observer returns an ArrayList<ContactObject> (contactsList) which I want to filter and sort before setting RecyclerView wit

sorting - 排序数组列表 Causing ClassCastException

My ViewModel observer returns an ArrayList<ContactObject> (contactsList) which I want to filter and sort before setting RecyclerView wit

问题描述

My ViewModel observer returns an ArrayList<ContactObject> (contactsList) which I want to filter and sort before setting RecyclerView with the modified ArrayList<ContactObject>.

Filter works as expected (it returns List<ContactObject> which I can cast to ArrayList<ContactObject>):

var filteredContactsList = contactsList.filter { contact -> !contact.sites.contains(siteId) } as ArrayList<ContactObject>

But I can't get any of the sort functions to work - I have tried:

var sortedList = contactsList.sortBy {(it as ContactObject).contactName} as ArrayList<ContactObject>

var sortedList = contactsList.sortedWith(compareBy { it.contactName }) as ArrayList<ContactObject>

But I get the following exception:

java.lang.ClassCastException: java.util.Arrays$ArrayList cannot be cast to java.util.ArrayList

So I'm trying to understand why these functions are returning a different type of list than .filter or if I am just using them incorrectly?

EDIT: I can get round this issue by converting it to ArrayList as below:

var sortedList = ArrayList<ContactObject>()
sortedList.addAll(contactsList.sortedWith(compareBy { it.contactName }))

However, I have to create the additional variable in my ViewModel, which I was hoping to avoid (i.e. I was going to pass contactsList.sortedWith(compareBy { it.contactName }) directly to the recyclerView)

How can I switch to the default thread pool in Spring Webflux / Reactor?

Reactor provides possibility to shift execution context to a different Scheduler like following:

Mono.just("test")
        .doOnNext(x -> System.out.println(currentThread().getName() + " " + x))
        .publishOn(MY_SCHEDULER)
        .doOnNext(x -> System.out.println(currentThread().getName() + " " + x))
        .subscribe();
-----------------------
main test
my-scheduler-1 test

How can I switch back to the main thread pool / scheduler that is used by default in Spring Webflux app (usually it appears with "main" in its name)?

标签： sortingkotlinarraylistclasscastexception

解决方案

如果打印返回类型的类名，您将知道 sortedWith 返回的对象的类是 java.util.Arrays$ArrayList 类型，而过滤器返回的对象是 java.util.ArrayList。因此，即使类名看起来相同，但是当您投射过滤器的输出时，它是成功的（它是 ArrayList 类型）但另一个失败（java.util.Arrays$ArrayList 具有相同的名称但嵌套在数组中班级）。

这两个类都扩展了 AbstractList 类，后者又实现了 List 接口。我认为正因为如此，您将类型视为 List，但具体实现不同。一个是 java.util.Arrays$ArrayList 而另一个是 java.util.ArrayList 。

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