Removing all zeros from an array list?

Question

So i currently have :

List<String> lineList = new ArrayList<String>();
String thisLine = reader.readLine();

while (thisLine != null) {
    lineList.add(thisLine);
    thisLine = reader.readLine();
}
System.out.println(lineList);

Which basically is reading a text file and returning the numbers in the text file. The output im getting is [0 6 13 0 0 75 33 0 0 0 4 29 21 0 86 0 32 66 0 0] which seems to be correct. However what I have to do is remove all the zeros without creating a new array. But will i have to convert this string arraylist to an integer array list to be able to do so? How could I only remove the zeros? Thanks!

Won't looping around the `lineList` once more solve your problem with `lineList.remove()` ? — ItachiUchiha, Feb 28 '14 at 06:32
See also [Remove all zeros from array](http://stackoverflow.com/q/8777217/456814). — , Aug 17 '14 at 07:41

score 4 · Answer 1 · answered Sep 21 '16 at 07:52

4

use removeAll() method to remove all zeros from an ArrayList...

lineList.removeAll(Collections.singleton(0));

answered Sep 21 '16 at 07:52

Jay Patel

2,341
2
22
43

Sanjeev · Answer 2 · 2014-02-28T06:51:09.167

3

You just need to modify your while loop like this:

 while (thisLine != null) {
       if(!thisLine.trim().equals("0")) {
           lineList.add(thisLine);
       }
        thisLine = reader.readLine();
    }

EDIT:

As per your input above code will not work as you are getting everything in a single line. You should use a Scanner to read it like this:

Scanner s = new Scanner(new File(<your file path>));
 List<Integer> lineList = new ArrayList<Integer>();

while(s.hasNextInt()){
    int i = s.nextInt();
     if(i!=0) {
         lineList.add(i);
     }
}

Hope this helps.

edited Feb 28 '14 at 06:51

answered Feb 28 '14 at 06:32

Sanjeev

9,876
2
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33

I like this solution because it avoids adding the 0's in the first place. – Daniel Feb 28 '14 at 06:34
I replaced my while loop with it yet it when i output lineList it still gives me the list with the zeros in it, any idea why? – user2778618 Feb 28 '14 at 06:41
whats the content in the file? – Sanjeev Feb 28 '14 at 06:43
exactly this "0 6 13 0 0 75 33 0 0 0 4 29 21 0 86 0 32 66 0 0" – user2778618 Feb 28 '14 at 06:47
ahhh it worked! thanks so much! Stayed up all night trying to troubleshoot this program. – user2778618 Feb 28 '14 at 06:53

score 0 · Answer 3 · answered Feb 28 '14 at 06:32

0

I'd to it in the while loop:

while (thisLine != null) {
    if(!thisLine.equals("0"){
        lineList.add(thisLine);
    }
    thisLine = reader.readLine();
}

answered Feb 28 '14 at 06:32

Toon Borgers

3,638
1
14
22

score 0 · Answer 4 · answered Feb 28 '14 at 06:39

0

Probably something like this would be sufficient ?

for(Iterator<String> it=lineList.iterator(); it.hasNext();) {
    String str = it.next();
    if(str.equalsIgnoreCase("0")) {
        it.remove();   
    }
}

answered Feb 28 '14 at 06:39

user1578544

23
3

Removing all zeros from an array list?

4 Answers4