arraylist

Get the Strings that occur exactly three times from Arraylist<String>

由 我只是一个虾纸丫 提交于 2019-12-14 03:45:11
问题 I have an ArrayList which contains some values with duplicates and elements that occur thrice, I want to collect those values that occur thrice specifically into another ArrayList like Arraylist<String> strings; //contains all strings that are duplicates and that occur thrice Here, I want to get only the Strings that occur thrice in another array list. Arraylist<String> thrice; //contains only elements that occur three times. Currently, I have a solution for dealing with duplicates but I

java.util.ConcurrentModificationException android after remove elements from array list

由 戏子无情 提交于 2019-12-14 03:39:34
问题 I have the folloing code in my android app: /** * callback executed after fetching the data. */ public void OnPointsFetch(ArrayList<Shop> result) { toggleLoader(false); this.shops = result; if(activeFilter == Constants.POINTS_FILTER_AVAILABLE){ for(Shop s : result){ if(s.getClientPoints().getPointsAvailable() == 0){ this.shops.remove(s); } } } else{ for(Shop s : result){ if(s.getClientPoints().getPointsSpent() == 0){ this.shops.remove(s); } } } ptsListAdapter.setCollection(this.shops);

How to remove the brackets [ ] from ArrayList#toString()?

由 喜你入骨 提交于 2019-12-14 03:39:32
问题 I have created an Array List in Java that looks something like this: public static ArrayList<Integer> error = new ArrayList<>(); for (int x= 1; x<10; x++) { errors.add(x); } When I print errors I get it errors as [1,2,3,4,5,6,7,8,9] Now I want to remove the brackets([ ]) from this array list. I thought I could use the method errors.remove("["), but then I discovered that it is just boolean and displays a true or false. Could somebody suggest how can I achieve this? Thank you in advance for

java arraylist iteration having a ClassCastException

由 自闭症网瘾萝莉.ら 提交于 2019-12-14 03:29:16
问题 I have model class: public class RecordSet { private DateRange daterange; private Master master; public DateRange getDaterange() { return daterange; } public void setDaterange(DateRange daterange) { this.daterange = daterange; } public Master getMaster() { return master; } public void setMaster(Master master) { this.master = master; } } public class DateRange { private Date ddate; public Date getDdate() { return ddate; } public void setDdate(Date ddate) { this.ddate = ddate; } } public class

How can I return a specific object (index) from an arraylist in Java?

由 萝らか妹 提交于 2019-12-14 03:23:33
问题 I created a class called Student and assigned it 3 values (StudentNumber, Course, Mark); I then assigned a created student (s) to an arrayList called studentsCourses. This way each student takes up an index in the array. But how do I get the students back OUT of the arrayList... if that makes sense? I have them stored, but I don't know how to recall the information so that I can see it. public static void main (String[]args){ ArrayList<Student> studentsCourses= new ArrayList<Student>();

Arraylist of objects - smallest value

由 天涯浪子 提交于 2019-12-14 02:36:13
问题 I have an arraylist of objects, and the objects have "double" values. I need to print out all the objects, and have the object with the highest value printed first, and the object with the lowest value last. I have also tried to use Collections to sort the arraylist and then print, but I can't seem to get it to work. My arraylist is: ArrayList<Transition> transitions = new ArrayList<Transition>(); When i tried to used Collections i used: Object minValue = Collections.min(transitions); Hope

How do read from a .txt file and put data into an array list of an object?

由 霸气de小男生 提交于 2019-12-14 01:42:24
问题 What I have written so far works from my current knowledge of basic arrays, but I just don't understand how to use an arraylist, or how to read from a file. What I have written so far works. Any links or advice to help fix my code to read from a file and use an arraylist would be greatly appreciated. Thank you. public class TestPackages { public static void main (String[] args) { Packages testPackages = new Packages(); testPackages.addPacket(1001, 7.37, "CA"); testPackages.addPacket(1002, 5

How to join elements of an ArrayList converting it to a string representation?

由 浪子不回头ぞ 提交于 2019-12-14 01:26:56
问题 I 've an ArrayList and to join all its elements with a separator in one string I m using... Dim s As String = String.Join(",", TryCast(myArrayList.ToArray(GetType(String)), String())) however, I would know if there is a smarter/shorter method to get the same result, or same code that looks better... Thank You in advance, Max 回答1: In Framework 4 it is really simple: var s = string.Join(",", myArrayList); In 3.5 with LINQ's extension methods: var s = string.Join(",", myArrayList.Cast<string>()

ArrayList 删除逻辑分析

由 夙愿已清 提交于 2019-12-14 01:16:55
ArrayList<String> list = new ArrayList<>(); list.add("1"); list.add("2"); list.add("3"); list.add("4"); list.add("5"); // list.add("6"); /** * 使用这种方式删除是不会报错的，但是会有个问题，就是数据删除不干净 * 也就是我们在删除数据的时候，数据会发生移动，所以有的位置上的数据就删不掉 * 当我们删除位置0上的元素时，2，3，4，5就会移动，此时位置1上的元素是3，所以下次删除的就是3，以此类推，在下一次就是5 * 所以删除完之后还剩下2，4 */ for(int i=0;i<list.size();i++){ list.remove(list.get(i)); }//2,4 /** * 使用这种方式遍历数据，只是一种java语法糖，java编译器会使用迭代器的方式重新实现，也就是下面的方式 * 使用这种方式，获取数据是根据cursor来进行获取的，如果我们只有两个元素，那么执行了list删除之后，cursor变成 * 1，然后hasNext比较cursor和size的大小，如果相同，返回就是false，所以就不会进入循环体 * 但是如果数量大于2，则删除一个之后，还会有两个，那么此时hasNext返回true（cursor为1，size为2

Why there is no ArrayList(T[] t) constructor?

由 让人想犯罪 __ 提交于 2019-12-14 00:29:49
问题 It is very common to initialize list by array of objects in such way: Foo[] objs = ...; ArrayList<Foo> list = new ArrayList<Foo>(Arrays.asList(objs)); I wonder, is there any reason why desiners of ArrayList didn't include constructor with array as parameter, so that it could be initialized like that: ArrayList<Foo> list = new ArrayList<Foo>(objs); May be it violates some principles, thread-safety or something else? 回答1: I don't know why it's not in the standard library, but Guava's Lists
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