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: A…
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 yo…
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 …
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”, i…
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, becau…
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 c…
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…