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?

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();
}

Arvind Kumar Avinash · Accepted Answer · 2020-12-11T17:16:18.023

2

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.

edited Dec 11 '20 at 17:16

answered Dec 11 '20 at 16:27

Arvind Kumar Avinash

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Shouldn't it be if (arr.length >= 2) – rishav prasher Dec 11 '20 at 16:29
@rishavprasher - The requirement is: `I need to store the second column data...` – Arvind Kumar Avinash Dec 11 '20 at 16:30
but after split length can we greater than 2. e.g. if it is 3 even then we have to store the number at the 2nd column right? – rishav prasher Dec 11 '20 at 16:32
@rishavprasher - You are right. Updated the answer. – Arvind Kumar Avinash Dec 11 '20 at 16:33
@ArvindKumarAvinash I posted a new code that how my code works when I tried your suggestion. Can you seee them? – Sabuha Kaya Dec 11 '20 at 17:09
@SabuhaRajanKaya - I've added an update on your request. Feel free to comment in case of any doubt/issue. – Arvind Kumar Avinash Dec 11 '20 at 17:17
@ArvindKumarAvinash Thank you so much that was a great help. Have a nice day:) – Sabuha Kaya Dec 11 '20 at 17:28

score 0 · Answer 2 · answered Dec 11 '20 at 16:28

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.

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

2 Answers2

Update: