So I have a list: For each number that matches, I have to get every permutation of the identifier. The lists I would need from my example would be as follows: Steps I am taking currently to solve the problem: Read in the list, place each value in an array ([a][12]) and place that in an ArrayList I then find
Tag: arraylist
Matrix multiplication in Java using 2D ArrayLists
I am trying to implement a simple matrix multiplication in Java, where I am storing the matrices in two-dimensional ArrayLists. It would seem the error is caused by the setting of matrix Result, inside the nested for loop, but I do not understand why. The code produces the result: when in fact it should be: Answer The Result is incorrectly
java.util.arraylist cannot be cast to java.lang.object[]
So in my code below, line marked with *** gives me the exception java.util.arraylist cannot be cast to java.lang.object[] I am trying to retrieve a list of users from backendless. I have created a list view that works when normally adding to list. but not when trying to get the response(Object) Answer what you are doing looks a bit long
Java invert a map
I need to invert an original map. which type is <Integer, String>, like {1 = A, 2 = A, 3 = B….}. I want to create a new map which is String to ArrayList because if 1 = A, and 2 = A, than I want to have something like this: A = [1， 2]. So how can I do
Latency in Iterator or foreach
i have one ArrayList that has a 1000 Insert SQL statement. but rather in execution time the latency of Iterator or (enhanced for loop) for this ArrayList take 1 minute . and my JFrame is not responding in this period. what can i do? Thanks Answer foreach internally uses iterator only, in order to handle bulk updates and inserts from
How to find the longest string object in an arrayList
Here is is my problem, I have to explain a lot, because it’s a quite complicated. I have created an arrayList<Word>, that contains strings as objects. In my case, I have three classes, all working together, that is supposed to represent a dictionary. The first class is called “Word”, it has a constructor, and has simple methodes like .length, adds
Removing Sublist from ArrayList
For simplicity, let’s say I have an ArrayList whose indices contain exactly one single-digit integer. For instance: I would like to filter out all occurrences of the sublist 6 0 6, such that the new list becomes: Is there any way of doing this? Using ListIterator doesn’t seem to work for me, because I have to consider three consecutive elements
Java – Slice any array at steps
In python we are able to do the following: Is there an equivalent to this in Java? I have been looking for this type of array slicing, but I have had no luck. Any help would be great, Thanks! Answer If you are using Java 8, then you can make use of streams and do the following: Outputs: [0, 3,
Creating a Matrix with ArrayLists
I want to create an ArrayList-matrix with n-rows and m-columns, for example I’ve already written a code for creating such a matrix but my code doesn’t display the values when I clear the list containing the column-data. Here is my Is there any possibility to clear the contents of intList without clearing the contents of mainList?? Answer When calling mainList.add(intList);
Getting only the first name in an array
I have an array list like this: ArrayList names = new ArrayList<>(); that stores people’s first and last names when they are entered in different textbooks. So when prompted to Joe Biden would be element number 1 then Barack Obama would be element number 2 in the array list. My question is that if it is possible to only get