I want to save a “AromaNorm” into NormalisasiT1 array, but i had a error : AWT-EventQueue-0 java.lang.NullPointerException Can you help me? Here the Code Answer you should initialize the array the array is null so it throws NPE.
Tag: arraylist
Add Mutlidimensional Array to ArrayList
I want to add a multidimensional Boolean Array to an ArrayList. How do I do that? Below is an simple example: public boolean[][] BooleanArray; ArrayList BooleanArrayList= new …
The property of the object calls removeAll(), why did it delete itself
public static void main(String[] args) { Dto dto = new Dto(); List aList = new ArrayList(); aList.add(1L); aList.add(2L); aList.add(3L); dto.setIdList(…
Java/Processing: A* graph node based game
I am trying to build a little ‘simulation’ game. This game has no real purpose, I am just making small little projects while I try and learn the in’s and out’s of some beginner programming. This is my goal: On the processing canvas, there are multiple ‘Nodes’ that represent…
Use HashSet to weed out duplicate values. List returns either empty or returns duplicate values
I am trying to remove duplicate values from an ArrayList using HashSet, so that city names aren’t returned more than once if they are the same… The List comes back either empty or still shows duplicate values. Was hoping someone could tell me where the error is in my code, so that no duplicate values ar…
Input Object into an array as a List in Java
I am a beginner in Java. I want to get input from the user to a 2D array, and convert into a list of objects. When I hardcoded the data, it could be done as this way but, I want to get this object arrays from the user input. When I am going to do this way, it was giving
Displaying an ArrayList alphabetically
I have a class written that takes a string, counts the occurrences of each letter within the string and then prints the occurrences of each. I want this to be displayed alphabetically, but not sure …
Sum int values in unsorted ArrayList based on dates
I’ve got a list of objects with LocalDateTime and int fields. Here is an example of an object from the list: How to check whether a sum of ints on a certain date (multiple entries for the same date possible) does not exceed some value for O(n) or better? forEach loop must be used, sorting is restricted.…
Constructor in a for loop
I’ve a beginner at java programming and I’ve been tasked at creating a database. The database is a bike store with a super class Bike and sub classes mountain bike, road bike. I also have a class …
Java Bubble Sort String ArrayList Object
Can someone find why this isn’t being sorted I can’t seem to find what I have wrong? The output that is being displayed is how I input them after each other thus the sort method isn’t working… Answer There are three errors: 1. It does i++ instead of i+1. i++ means: return i then increm…