convert String to Array in Java

Question

I have a txt file like this:

5
1
3
6
9

I want to read them using java and store all of the numbers into a array.How do I do that? read them in as string and convert to arrray? (how to convert?) the file only contain ints.

I tried read them into a string and use this to convert

 static public int[] strToA(String str)
{
    int len = str.length();
    int[] array = new int[len];
    for (int i = 0; i < len; i++)
    {
        array[i] = Integer.parseInt(str.substring(i,i+1));
    }
    return array;
}

Answer 1

Scanner can help you read your file, and you can use a List or something else to store the info.

After that, you can use this List to convert your Array .

Answer 2

public static Integer[] read2array(String filePath) throws IOException {
    List<Integer> result = new ArrayList<Integer>();
    RandomAccessFile randomAccessFile = new RandomAccessFile(filePath, "r");
    String line = null;
    while(null != (line = randomAccessFile.readLine())) {
        result.add(new Integer(line));
    }
    randomAccessFile.close();
    return result.toArray(new Integer[result.size()]);
}

Answer 3

Code would be something like this. This is untested code and may have Syntax errors.

Path file = "yourfile";
// open file
try (InputStream in = Files.newInputStream(file);
    BufferedReader reader =
      new BufferedReader(new InputStreamReader(in))) {
    String line = null;
    intArr = new int[10]; // bad code could fail if file has more than 10
    int i = 0;
    while ((line = reader.readLine()) != null) {
        intArr[i++] = Integer.parseInt(line); // parse String to int
    }
} catch (IOException x) {
    System.err.println(x);
}

To use List instead of array change line

intArr = new int[10];

to

List intArr = new ArrayList();

Code would be something like

    List intArr = new ArrayList();
    while ((line = reader.readLine()) != null) {
        intArr.add(Integer.parseInt(line)); // parse String to int
    }