Week 3: Objects, files and exceptions/4. Remove negative numbers - get, remove

Write the method

void removeNegatives(ArrayList<Integer> numnbers) 

...which removes all numbers less than zero from the list.

Tip: the for loop may not work reliably if the iterated structure changes during loop execution 
- you should use another way to iterate through the list instead.



Example method call:
public static void main(String[] parameters){
    ArrayList<Integer> numbers = new ArrayList<>();
    numbers.add(1);
    numbers.add(-2);
    numbers.add(-5);
    numbers.add(10);
    System.out.println(numbers);
    removeNegatives(numbers);
    System.out.println(numbers);
}


Program outputs:
[1, -2, -5, 10]
[1, 10]



============================


import java.util.Random;
import java.util.ArrayList;

public class Test{
    public static void main(String[] args){
        final Random r = new Random();
        
        
        int[][] s = {{1,-2,3}, {10,-20,30,-40}, {-2,4,-6,8,-10}, {-9,-1,-8,2,7,3,-6,-4}};
        
        for (int[] pa : s) {
            ArrayList<Integer> lista = new ArrayList<>();
            for (int l : pa) lista.add(l);
            
            System.out.println("List before: ");
            System.out.println("" + lista);
            System.out.println("List after: ");
            removeNegatives(lista);
            System.out.println(lista);
            System.out.println("");
            
        }
    }
    



    // ADD
    public static void removeNegatives(ArrayList<Integer> numbers) {
        for (int i = 0; i < numbers.size(); i++) {
            if (numbers.get(i) < 0) {
                numbers.remove(i);
                // because we remove the current idx
                // adjust i by 1 (like as if we finished the previous 'i')
                // System.out.println(i);
                i--;
                // System.out.println(i);
            }
        }
    }




}








// Test1
// List before: 
// [1, -2, 3]
// List after: 
// 1
// 0
// [1, 3]

// List before: 
// [10, -20, 30, -40]
// List after: 
// 1
// 0
// 2
// 1
// [10, 30]

// List before: 
// [-2, 4, -6, 8, -10]
// List after: 
// 0
// -1
// 1
// 0
// 2
// 1
// [4, 8]

// List before: 
// [-9, -1, -8, 2, 7, 3, -6, -4]
// List after: 
// 0
// -1
// 0
// -1
// 0
// -1
// 3
// 2
// 3
// 2
// [2, 7, 3]








List before: 
[1, -2, 3]
List after: 
[1, 3]

List before: 
[10, -20, 30, -40]
List after: 
[10, 30]

List before: 
[-2, 4, -6, 8, -10]
List after: 
[4, 8]

List before: 
[-9, -1, -8, 2, 7, 3, -6, -4]
List after: 
[2, 7, 3]