Turn text file into array

Try this :

Class

 Class DataClass
 {
   public int first; // Deliberately public 
   public int second;

   public DataClass(int val1, int val2){
   this.first = val1;
   this.second = val2;
   }
 }

Code

    public static void loadList() {

    ArrayList<DataClass> pairList = new ArrayList<DataClass>();
    BufferedReader br = new BufferedReader(new FileReader("./data.txt"));
    String line;
    while ((line = br.readLine()) != null) {
        String args[] = line.split(":");
        int first = Integer.valueOf(args[0]);
        int second = Integer.valueOf(args[1]);
        DataClass valPair = new DataClass(first,second);
        pairList.add(valPair);
        System.out.println(valPair.first + " : " + valPair.second);
    }
    br.close();
 }

Make sure you have proper try catch statements

Doing a bit of Java-magic here:

  public static class DataValue {

    protected final int first, second;

    public DataValue(int first, int second) {
      this.first = first;
      this.second = second;
    }
  }

  public static List<DataValue> loadList() throws FileNotFoundException, IOException {
    final List<DataValue> result = new LinkedList<>();
    try (BufferedReader br = new BufferedReader(new FileReader("./data.txt"))) {
      String line;
      String args[];
      while ((line = br.readLine()) != null) {
        try {
          args = line.split(":");
          final int first = Integer.parseInt(args[0]);
          final int second = Integer.parseInt(args[1]);
          System.out.println(first + " : " + second);
          result.add(new DataValue(first, second));
        } catch (NumberFormatException | NullPointerException | ArrayIndexOutOfBoundsExceptione) {
          System.out.println("Unable to process line: " + line);
        }
      }
    }
    return result;
  }

First: this is Java 7 code, it doesn't work with Java 6.

• One of the Object Oriented principle is: keep your data together. Therefore this approach above uses a special data holder class, to make sure you do not accidentally confuse numbers from different lines later on.

• Using the try (stream) {} concept form Java 7 ensures that the stream is properly closed under all circumstances. In your code the stream would be left half-open if reading from it would cause an Exception to be thrown.

• If you work with dynamic data from "outside", you must check it properly. You never know if anyone accidentally or on purpose put errors into the file. This is what my inner try-catch does.

• Using an ArrayList is not a good idea in your case, because it has a fixed size and your data probably is not of a fixed size, therefore the internal storage would have to be re-created a few times during reading. A linked list performs perfectly in this case (but poorly if you do myList.get(index)).
  Later you can use the Java for-each loop like this:
  for (DataValue value : myList) { System.out.println(value.first + " : " + value.second); }

• You should avoid to declare variables inside a loop unless you have to. And if you have to, use final to tell the JIT that it can use full optimization on these variables.

• Integer.parseInt(string) is the correct way to transform a string into an Integer. Make sure to read the definition on when this throws an exception!

try this!

public static void loadList() throws NumberFormatException, IOException {
        BufferedReader br = new BufferedReader(new FileReader("./data.txt"));
        String line;
        while ((line = br.readLine()) != null) {
            if(line.trim().length() == 0)
                continue;
            String args[];
            args = line.split(":");
            int first = Integer.parseInt(args[0]);
            int second = Integer.parseInt(args[1]);
            System.out.println(first + " : " + second);
        }
        br.close();
    }