Java Reading a txt that has different numbers in its column file and store data in an arraylist

Question

Hello Guys I have a txt file below, I need to store the second column data but it gives me an error since some lines have 1 some have 2 and some have 3 input in each line. How can I solve that problem?

5
3 4
3 4
3 3
3 4
3 3
3 4
3 3
3 2
3 4
3 3
3 2
3 1
3 4
3 3
3 2
3 1
3 0
1
2
5 3 4
3 4
3 4
3 3
3 4
3 3
3 4
3 3
3 2
3 4
3 3
3 2
3 1
3 4
3 3
3 2
3 1
3 0
1
2
5 4 6
4 4
4 4
4 4
4 4
4 4
4 4
4 3
4 3
4 3
4 3
4 4
4 4
1
2
5 4 6
0

Here is what I did, I tried to differentiate as the size and in the other way but still cant get the answer...

String line = "";

ArrayList<String> numbers= new ArrayList<String>();

try {

    String sCurrentLine;
    br = new BufferedReader(new FileReader("input1.txt"));
    int n = 0;

    while ((sCurrentLine = br.readLine()) != null) {
        String[] arr = sCurrentLine.split(" ");
        int size = arr.length;

        List<String> list = ConvertToList.convertArrayToList(arr);
        List<Integer> listOfInteger = convert.convertStringListToIntList(list, Integer::parseInt);
        if (list.size() == 2) {
            line.split("\\s+");
            numbers.add(line.split("\\s+")[0]);
            System.out.println(numbers);
        }
    }
} catch(Exception e) {
    e.printStackTrace();
}

Answer 1

You do not need to split the line again. When you split the line first time, check if the length of the resulting array is 2 . If yes, add arr[1] to numbers .

while ((sCurrentLine = br.readLine()) != null) {
    String[] arr = sCurrentLine.split(" ");                
    if (arr.length >= 2) {
        numbers.add(arr[1]);
        System.out.println(numbers);
    }
}

Update:

Based on your comment, I am providing you following code which uses your lists:

while ((sCurrentLine = br.readLine()) != null) {
    String[] arr = sCurrentLine.split(" ");
    List<String> list = ConvertToList.convertArrayToList(arr);
    List<Integer> listOfInteger = convert.convertStringListToIntList(list, Integer::parseInt);
    if (listOfInteger.size() >= 2) {
        numbers.add(listOfInteger.get(1));
    }          
}
System.out.println(numbers);

You can keep System.out.println(numbers); inside or outside the while loop depending on how you want to print numbers .

Answer 2

If you want to read and save only the second column than you get the data in second column by using the index 1. (After your while loop.)

String secondCol = sCurrentLine.split(" ")[1];

In case you don't have a value in 2 column than it will throw and exception which you should handle with simple try catch. Finally convert it to int and store in your list. with following.

listOfInteger.add(Integer.parseInt(secoundCol));

Hopefully it will work.