How to remove empty elements from arrayList in this code

Question

I experienced a problem with my code where I can not remove empty elements in my arrayList. It ends up returning [1, 2, 3, 0, 8, , 12 , , 34 , 0 ] however those empty elements do not get removed after numerous attempts

public static ArrayList<String> readNumbers() {
    Scanner inFile = null;
    File file = null;
    String filePath = (JOptionPane.showInputDialog("Please enter a file path"));
    int size = 0;
    ArrayList<String> result = new ArrayList<String>();

    try {
        file = new File(filePath);
        inFile = new Scanner(file);
        int skippedCounter = 0;

        for(int i = 0; inFile.hasNext(); i++){
            if(inFile.hasNextInt())
                result.add(inFile.next());
            else{
                String strOut = "";
                String data = inFile.nextLine();

                for(int j = 0; j <= data.length() - 1; j++){
                    if(!Character.isLetter(data.charAt(j))){
                        strOut += data.charAt(j);
                    }
                    else
                        skippedCounter++;
                }
                if(!strOut.isEmpty())
                    result.add(strOut);
            }
        }
    } 
    catch (FileNotFoundException e) {
        System.out.println("File not found");
    } 
    catch(NumberFormatException e){
        System.out.println("Not a number");
    }
    finally {
        inFile.close();
    }
    int count = 0;
    result.removeIf(String::isEmpty);

    return result;
}

Erwin Bolwidt · Accepted Answer · 2019-04-01 02:50:15Z

1

String::isEmpty() only checks if the length of the string is zero. It doesn't return true if your string consists of only spaces or other whitespace.

You can do a String.trim() first and then check for String.isEmpty().

result.removeIf(s -> s.trim().isEmpty());

answered Apr 1, 2019 at 2:50

Erwin Bolwidt

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2 Comments

Kevin Over a year ago

Hi this fixed it and I appreciate it, what does the -> mean?

Erwin Bolwidt Over a year ago

It's a lambda. It's short for new Function<String,String>() { public String apply(String s) { return s.trim().isEmpty(); } }, basically.

liuchuanhung · Accepted Answer · 2019-04-01 02:52:55Z

0

I believe in Java 8 and up, you can do something like this to remove all empty values from list: results.removeIf(item -> != StringUtils.isEmpty(item));

answered Apr 1, 2019 at 2:52

liuchuanhung

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Comments

Suraj Kumar · Accepted Answer · 2019-04-01 04:12:21Z

0

You can try:

List<Integer> listWithNulls = Arrays.asList(1,null, 2, 3, null, 4);

List<Integer> listWithoutNulls = listWithNulls.stream().filter(Objects::nonNull).collect(Collectors.toList());

edited Apr 1, 2019 at 4:12

Suraj Kumar

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answered Apr 1, 2019 at 3:16

nha dao duc

1

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