arraylist

不断的向数组的中间插入数据，ArrayList和LinkedList哪个快

由 旧时模样 提交于 2019-12-22 03:26:03
java中的ArrayList 、List、LinkedList、Collection关系详解 一、基础介绍（Set、List、Map） Set（集）：集合中的元素不按特定方式排序，并且没有重复对象。他的有些实现类能对集合中的对象按特定方式排序。 List（列表）：集合中的元素按索引位置排序，可以有重复对象，允许按照对象在集合中的索引位置检索对象。 Map（映射）：集合中的每一个元素包含一对键对象和值对象，集合中没有重复的键对象，值对象可以重复。他的有些实现类能对集合中的键对象进行排序。 二、基本接口和类型 1、Iterator接口 该接口允许遍历集合中的所有元素，一共有三个方法： public boolean hasNext()：判断是否还有下一个元素。 public Object next()：取得下一个元素，注意返回值为 Object，可能需要类型转换。如果不再有可取元素，则抛出NoSuchElementException异常。在使用该方法之前，必须先使用hasNext()方法判断。 public void remove()：删除当前元素，很少用。 2、Collection接口 该接口是Set和List的父接口，主要提供了下面的方法： public boolean add(Object?o)：往集合中添加新元素。添加成功，返回true，否则返回false。 public

ArrayList<> vs ArrayList<Integer>

由 我们两清 提交于 2019-12-22 02:00:53
问题 What is the difference in the two following declarations of an ArrayList? ArrayList<Integer> nunbers = new ArrayList<Integer>(); vs ArrayList<Integer> nunbers = new ArrayList<>(); Is one of them preferred over the other? 回答1: The second one has its type parameter inferred , which is a new thing in Java 7. <> is called "the diamond". Also note that type inference itself is not new in Java, but the ability to infer it for the generic class being instantiated is new. Compilers from releases

Camel Splitter Parallel Processing Array List - Concurrency Access Issue

由 守給你的承諾、 提交于 2019-12-22 01:19:40
问题 Using Camel to split an ArrayList and process each item in parallel up to 10 threads. Following is the config. Thread pool profile is set to max thread count =10. <camel:route id="ReportsRoute"> <camel:from uri="direct:processReportsChannel" /> <camel:to uri="bean:reportRepository?method=getPendingTransactions" /> <camel:split parallelProcessing="true" executorServiceRef="ReportThreadPoolProfile"> <camel:simple>${body}</camel:simple> <camel:doTry> <camel:to uri="direct:processReportChannel" /

How to convert nested List into multidimensional array?

由 天大地大妈咪最大 提交于 2019-12-22 00:06:54
问题 In Java I want to convert a nested List which contains at the deepest level a uniform type into an multidimensional array of that type. For example, ArrayList<ArrayList<ArrayList<ArrayList<String>>>> into String[][][][] . I've tried several things and I only can obtain an array of objects like Object[][][][] . For 'simple lists' it seems that Apache Commons Lang does the work but I cannot figure out for nested cases. Update: In order to obtain a multidimensional array of Object type I'm using

Adding multiple items at once to ArrayList in Java [duplicate]

由 北城余情 提交于 2019-12-21 23:28:38
问题 This question already has answers here : Add multiple items to already initialized arraylist in java (6 answers) Closed 2 years ago . How can I add multiple items at once to an ArrayList? ArrayList<Integer> integerArrayList = new ArrayList(); Instead of: integerArrayList.add(1) integerArrayList.add(2) integerArrayList.add(3) integerArrayList.add(4) ... I would like to: integerArrayList.add(3, 1, 4, 2); So that I wont have to type so much. Is there a better way to do this? 回答1: Use Collections

'java.lang.String android.content.Context.getPackageName()' on a null object reference

由 北城以北 提交于 2019-12-21 20:59:17
问题 My alarmManager is in the MainActivity it fires every 30 second to the MyReceiver class then from it I start the GetLLRD IntentService class. Thereafter, I am sending a request from the onHandleIntent method to the Server following which I am getting a Response. Now I want to achieve the following, every time the alarmManager fires in the MainActivity I want to pass the Intent from the Response from the Server in the GetLLRD class to the Map class. I have tried it twice with the intent's code

For Each Loop Question

由 核能气质少年 提交于 2019-12-21 20:48:59
问题 I'm having problems understanding a for-each loop. I am familiar w/ the typical structure of a for-each, where there is built in counter and assignment statement to each element. However, in the code below what does the "new" keyword imply? Does it execute only once? for(Integer item : new ArrayList<Integer>(myCollection)){ myCollection.add(first.intValue() + item.intValue()); } Is this equivalent to the following for loop? for(int ctr = 0; ctr < myCollection.size(); ctr++){ Integer temp =

Arraylist can't compare objects after they are loaded from disk

由 瘦欲@ 提交于 2019-12-21 20:18:38
问题 To make it easy, lets say I have an arraylist allBooks containing class "books" and an arraylist someBooks containing some but not all of the "books". Using contains() method worked fine when I wanted to see if a book from one arraylist was also contained in another. The problem was that this isn't working anymore when I save both of the Arraylists to a .bin file and load them back once the program restarts. Doing the same test as before, the contains() returns false even if the compared

ArrayList cannot be cast to custom class extending ArrayList

由 ≯℡__Kan透↙ 提交于 2019-12-21 17:42:05
问题 I have class mentioned below: public class JsonHistoryList extends ArrayList<JsonHistory> implements Serializable{} I wish to pass it through intent using timerService.putExtra(TimerService.ACTIVITY_LIST_ARG, activities); But after I receive it (way below) JsonHistoryList temp = (JsonHistoryList) intent.getSerializableExtra(TimerService.ACTIVITY_LIST_ARG); in my service it gives me exception: Caused by: java.lang.ClassCastException: java.util.ArrayList cannot be cast to com.epstim.captime

JNI - java ArrayList conversion to c++ std::string*

由 ＊爱你＆永不变心＊ 提交于 2019-12-21 17:33:19
问题 I am trying to make a data conversion with JNI in c++. I have come into trouble working with java 's ArrayList of strings , since I have not been able to convert such a data into a c++ vector or std::string* . I would like to know how this conversion can be made without sacrificing too much performance, if possible. Any ideas would be appreciated. 回答1: I don't know if this fits your performance requirements, but it may be a good start. For both options assume that jobject jList; is your
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