What does the equivalence to this Python list look like in Java?

Question

I'm trying to learn Java, more specifically I'm trying to learn a couple of differences when working with arrays and lists. Right now I'm trying to understand how I can implement this line list += [i]*i in Java.

Sum = 5000
list = [0, 0]
x = 1
while len(list) < Sum:
    list += [x]*x
    x += 1

I've tried a lot of different methods but I can't seem to find a way. The results I get in Java with the methods I've tried are all wrong.

Answer 1

Directly translated (with the helpful utility function java.util.Collections.nCopies ) it becomes something like:

import java.util.*;

int Sum = 5000;  //Following the naming convention in Java (and Python) "Sum" should be lowercase

ArrayList<Integer> list = new ArrayList<Integer>();
//Alternatively: List<Integer> list = new ArrayList<Integer>();

list.add(0);
list.add(0);

int x = 1;
while (list.size() < Sum) {
    list.addAll(Collections.nCopies(x, x));
    x += 1;
}

Answer 2

Use a combination of for loop, add method and a ArrayList data structure. It could look something like below.

List<Integer> nums = new ArrayList<>();
int x = 1;
while (condition){
  for (int i=0; i<x; i++) {
    nums.add(x);
  }
  x+=1
}