All Questions
2,419
questions
756
votes
11
answers
1.4m
views
Convert list to array in Java [duplicate]
How can I convert a List to an Array in Java?
Check the code below:
ArrayList<Tienda> tiendas;
List<Tienda> tiendasList;
tiendas = new ArrayList<Tienda>();
Resources res = this....
- 12.1k
621
votes
17
answers
646k
views
Why do I get an UnsupportedOperationException when trying to remove an element from a List?
I have this code:
public static String SelectRandomFromTemplate(String template,int count) {
String[] split = template.split("|");
List<String> list=Arrays.asList(split);
Random r = ...
- 206k
581
votes
40
answers
1.0m
views
How do I remove repeated elements from ArrayList?
I have an ArrayList<String>, and I want to remove repeated strings from it. How can I do this?
- 5,981
500
votes
12
answers
478k
views
ArrayList vs List<> in C#
What is the difference between ArrayList and List<> in C#?
Is it only that List<> has a type while ArrayList doesn't?
- 14.3k
464
votes
21
answers
1.3m
views
How to sort a List/ArrayList?
I have a List of doubles in java and I want to sort ArrayList in descending order.
Input ArrayList is as below:
List<Double> testList = new ArrayList();
testList.add(0.5);
testList.add(0.2);
...
- 4,821
400
votes
10
answers
497k
views
How to avoid "ConcurrentModificationException" while removing elements from `ArrayList` while iterating it? [duplicate]
I'm trying to remove some elements from an ArrayList while iterating it like this:
for (String str : myArrayList) {
if (someCondition) {
myArrayList.remove(str);
}
}
Of course, I get ...
- 8,627
299
votes
9
answers
203k
views
Java List.add() UnsupportedOperationException
I try to add objects to a List<String> instance but it throws an UnsupportedOperationException.
Does anyone know why?
My Java code:
String[] membersArray = request.getParameterValues('members')...
- 4,404
268
votes
9
answers
203k
views
How to randomize two ArrayLists in the same fashion?
I have two arraylist filelist and imgList which related to each other, e.g. "H1.txt" related to "e1.jpg". How to automatically randomized the list of imgList according to the randomization of fileList?...
- 15.5k
260
votes
16
answers
268k
views
When to use a linked list over an array/array list?
I use a lot of lists and arrays but I have yet to come across a scenario in which the array list couldn't be used just as easily as, if not easier than, the linked list. I was hoping someone could ...
- 7,522
211
votes
9
answers
543k
views
How to split() a delimited string to a List<String>
I had this code:
String[] lineElements;
. . .
try
{
using (StreamReader sr = new StreamReader("TestFile.txt"))
{
String line;
while ((...
168
votes
1
answer
301k
views
What is the difference between List and ArrayList? [duplicate]
I've been using ArrayList recently in my android project at the office and I'm a bit confused between List and ArrayList, what is the difference of the two and what should I use?
Also I saw some ...
- 3,093
116
votes
1
answer
36k
views
Why is Java's AbstractList's removeRange() method protected?
Does anyone have any idea, why removeRange method in AbstractList (and also in ArrayList) is protected? It looks like a quite well-defined and useful operation, but still, to use it, we're forced to ...
- 36.4k
110
votes
9
answers
275k
views
List<String> to ArrayList<String> conversion issue
I have a following method...which actually takes the list of sentences and splits each sentence into words. Here is it:
public List<String> getWords(List<String> strSentences){
allWords = ...
- 1,261
102
votes
4
answers
127k
views
Convert an array into an ArrayList [duplicate]
I'm having a lot of trouble turning an array into an ArrayList in Java. This is my array right now:
Card[] hand = new Card[2];
"hand" holds an array of "Cards". How this would look like as an ...
- 1,177
101
votes
20
answers
242k
views
Option to ignore case with .contains method?
Is there an option to ignore case with .contains() method?
I have an ArrayList of DVD object. Each DVD object has a few elements, one of them is a title. And I have a method that searches for a ...
- 1,301
99
votes
23
answers
121k
views
In Java how do you sort one list based on another?
I've seen several other questions similiar to this one but I haven't really been able to find anything that resolves my problem.
My use case is this: user has a list of items initially (listA). They ...
- 1,211
82
votes
14
answers
196k
views
Convert List<String> to List<Integer> directly
After parsing my file " s" contains AttributeGet:1,16,10106,10111
So I need to get all the numbers after colon in the attributeIDGet List. I know there are several ways to do it. But is there any ...
- 19.4k
78
votes
6
answers
212k
views
How to remove the last element added into the List?
I have a List in c# in which i am adding list fields.Now while adding i have to check condition,if the condition satisfies then i need to remove the last row added from the list.
Here is my sample ...
- 821
77
votes
10
answers
112k
views
find out the elements of an arraylist which is not present in another arraylist
I have to find a best way to find out that elements which is not presented in the second arraylist.
suppose
Arraylist a,b,
Arraylist a={1,2,3,4,5};
Arraylist b={2,3,4};
So basically what I want ...
- 2,350
69
votes
8
answers
175k
views
How does one convert a HashMap to a List in Java?
In Java, how does one get the values of a HashMap returned as a List?
- 13.3k
68
votes
4
answers
64k
views
How to convert an ArrayList to a strongly typed generic list without using a foreach?
See the code sample below. I need the ArrayList to be a generic List. I don't want to use foreach.
ArrayList arrayList = GetArrayListOfInts();
List<int> intList = new List<int>();
/...
- 30.7k
68
votes
4
answers
224k
views
Check if a String is in an ArrayList of Strings
How can I check if a String is there in the List?
I want to assign 1 to temp if there is a result, 2 otherwise.
My current code is:
Integer temp = 0;
List<String> bankAccNos = new ArrayList&...
- 1,584
56
votes
2
answers
159k
views
Dynamically adding elements to ArrayList in Groovy
I am new to Groovy and, despite reading many articles and questions about this, I am still not clear of what is going on.
From what I understood so far, when you create a new array in Groovy, the ...
- 966
55
votes
15
answers
260k
views
Java Compare Two List's object values?
I have two list **ListA<MyData> listA = new ArrayList<MyData>()** and ListB<MyData> listB = new ArrayList<MyData>() both contain object of type MyData and MyData contain these ...
user2309806
54
votes
2
answers
32k
views
UnsupportedOperationException in AbstractList.remove() when operating on ArrayList
ArrayList's list iterator does implement the remove method, however, I get the following exception thrown:
UnsupportedOperationException at java.util.AbstractList.remove(AbstractList.java:144)
By ...
- 28k
54
votes
6
answers
30k
views
ArrayList vs List<object>
I saw this reply from Jon on Initialize generic object with unknown type:
If you want a single collection to
contain multiple unrelated types of
values, however, you will have to use
List<...
- 8,257
52
votes
7
answers
58k
views
Incompatible types List of List and ArrayList of ArrayList
The below line gives me error :
Incompatible Types.
List<List<Integer>> output = new ArrayList<ArrayList<Integer>>();
What is the reason?
EDIT
I understand if I change my ...
- 23.8k
47
votes
8
answers
28k
views
c# When should I use List and when should I use arraylist?
As the title says when should I use List and when should I use ArrayList?
Thanks
- 999
46
votes
1
answer
102k
views
What is the difference between an Array, ArrayList and a List? [duplicate]
I am wondering what the exact difference is between a Array, ArrayList and a List (as they all have similar concepts) and where you would use one over the other.
Example:
Array
For the Array we can ...
- 577
41
votes
10
answers
232k
views
Simple way to compare 2 ArrayLists
I have 2 arraylists of string object.
List<String> sourceList = new ArrayList<String>();
List<String> destinationList = new ArrayList<String>();
I have some logic where i ...
- 1,267
37
votes
5
answers
43k
views
ArrayList vs LinkedList from memory allocation perspective
I need to store a large amount of information, say for example 'names' in a java List. The number of items can change (or in short I cannot predefine the size). I am of the opinion that from a memory ...
- 998
35
votes
7
answers
6k
views
Why is an ArrayList of ArrayLists not multidimensional?
I recently appeared for an interview in which the interviewer asked me a question regarding Arrays and ArrayList.
He asked me if an array of arrays can be multidimensional, then why is an ArrayList ...
- 1,759
34
votes
7
answers
114k
views
Java ArrayList clear() function
Let's say I have a ArrayList<String> data;
I'm adding some data into this Array, using data.add() function.
Let's say I've added 10 Strings into this array. The size of the array is 10 now.
...
- 3,957
34
votes
6
answers
28k
views
Remove duplicates from List using Guava
How can we remove duplicates from List with the help of Guava api?
Currently I am following this:
private List<T> removeDuplicate(List<T> list){
return new ArrayList<T>(new ...
- 13k
31
votes
7
answers
47k
views
Reason for - List list = new ArrayList(); [duplicate]
I have seen code like this many times:
List<String> list = new ArrayList<String>();
Why do people take the parent of ArrayList (and other classes) instead of the type of the generated ...
- 10.3k
31
votes
3
answers
46k
views
Merge 3 arraylist to one
I want to merge down 3 arraylist in one in java. Does anyone know which is the best way to do such a thing?
- 2,659
30
votes
6
answers
64k
views
Finding out if a list of Objects contains something with a specified field value?
I have a list of DTO received from a DB, and they have an ID. I want to ensure that my list contains an object with a specified ID. Apparently creating an object with expected fields in this case won'...
- 2,880
30
votes
6
answers
57k
views
Why can't you have a "List<List<String>>" in Java? [duplicate]
In Java, why doesn't the following line of code work?
List<List<String>> myList = new ArrayList<ArrayList<String>>();
It works if I change it to
List<ArrayList<String&...
- 11.1k
30
votes
9
answers
14k
views
Benefits of arrays
As I see it, the advantages of a list over an array are pretty obvious:
Generics provide more precise typing: List<Integer>, List<? extends Number>, List<? super Integer>.
A List ...
- 113k
28
votes
7
answers
4k
views
Is there a way to avoid loops when adding to a list?
I was wondering a code like this:
List<String> list = new ArrayList<String>();
for(CustomObject co : objects) {
list.add(co.getActualText());
}
Can it be written differently? I ...
- 19.1k
28
votes
5
answers
255k
views
List<Object> and List<?>
I have two questions, actaully...
First off, Why cant I do this:
List<Object> object = new List<Object>();
And second, I have a method that returns a List<?>, how would I turn that ...
- 451
28
votes
2
answers
54k
views
Modifier static is only allowed in constant variable declarations
I have an inner class that stores the info of the controls I'm using for a game, now I want to store a static ArrayList in it that holds all the names of the controls. But I am getting this error: &...
- 2,290
28
votes
7
answers
117k
views
convert string to arraylist <Character> in java
How to convert a String without separator to an ArrayList<Character>.
My String is like this:
String str = "abcd..."
I know one way of doing this is converting the String to char[] first, and ...
- 1,024
26
votes
4
answers
94k
views
new ArrayList<int>() failing in Java
I have the following code:
List<int> intList = new ArrayList<int>();
for (int index = 0; index < ints.length; index++)
{
intList.add(ints[index]);
}
It gives me an error...
...
- 24k
26
votes
7
answers
104k
views
Check if an ArrayList contains a given object
Assuming I have class like this:
class A {
int elementA;
int elementB
}
I also have an ArrayList like this: ArrayList<A> listObj.
How can I check if that list contains an object using ...
- 401
25
votes
4
answers
68k
views
How to remove common values from two array lists
How can we remove common values from two ArrayLists?
Let’s consider I have two Arraylist as shown below:
ArrayList1 = [1,2,3,4]
ArrayList1 = [2,3,4,6,7]
I would like to have result as:
...
- 3,336
25
votes
6
answers
59k
views
What is a List vs. an ArrayList? [duplicate]
What are the fundamental differences between the two objects? Is one more efficient? Does one have more methods?
- 873
25
votes
3
answers
47k
views
How do I initialize a two-dimensional List statically?
How can I initialize a multidimensional List statically?
This works:
List<List<Integer>> list = new ArrayList<List<Integer>>();
But I'd like to init the list with some ...
- 6,569
24
votes
4
answers
49k
views
Moving data from a HashSet to ArrayList in Java
I have the following Set in Java:
Set< Set<String> > SetTemp = new HashSet< Set<String> >();
and I want to move its data to an ArrayList:
ArrayList< ArrayList< String &...
- 618
24
votes
2
answers
27k
views
ArrayList vs the List returned by Arrays.asList() [duplicate]
The method Arrays.asList(<T>...A) returns a List representation of A.
The returned object here is a List backed by an array, but is not an ArrayList object.
I'm looking for the differences ...
- 4,891