Leading zero is kept in arraylist ---

Question

Hello,
Running the program below should remove all zeros from an arraylist; yet, the leading zero still appears in the output. Any explanation would be most helpful ... Thanks
import java.util.ArrayList;
public class Example
public static ArrayList<Integer> nums = new ArrayList<Integer>();
public static void numQuest()
int k = 0;
Integer zero = new Integer(0);
nums.add(0);
nums.add(0);
nums.add(4);
nums.add(2);
nums.add(5);
nums.add(0);
nums.add(3);
nums.add(0);
while ( k < nums.size())
if (nums.get(k).equals(zero))
nums.remove(k);
k++;
System.out.print("contents of nums: " + nums );
System.out.print("\n");
public static void main (String[] args)
numQuest();

Answer 1

import java.util.*;
public class Example {
    public static void main (String[] args) {
        List<Integer> numbers = new ArrayList<Integer>();
        Collections.addAll(numbers, 0, 0, 4, 2, 5, 0, 3, 0);
        System.out.println("before: " + numbers);
        numbers.removeAll(Arrays.asList(0));
        System.out.println("after: " + numbers);
}looping over a collection while removing elements (which shifts the rest up) is a bad idea, unless you are going backwards from end to beginning.
But using removeAll is even easier!
The manual solution is to use an iterator and its remove method:
import java.util.*;
public class Example {
    public static void main (String[] args) {
        List<Integer> numbers = new ArrayList<Integer>();
        Collections.addAll(numbers, 0, 0, 4, 2, 5, 0, 3, 0);
        System.out.println("before: " + numbers);
        for(Iterator<Integer> i = numbers.iterator(); i.hasNext(); ) {
            if (i.next().equals(0)) {
                i.remove();
        System.out.println("after: " + numbers);
}