Question

I'm trying to parse a text file that looks like:

1     400.0     -1.6533271     5.7718643 
2     401.0     -1.6596413     5.7751263 
3     402.0     -1.6656540     5.7781345 
4     403.0     -1.6713679     5.7808704 
5     404.0     -1.6767864     5.7833152

So I've made the following method to get each of those values separately:

void parseFile(String filepath) throws FileNotFoundException, IOException {

    FileReader filereader = new FileReader(filepath);
    BufferedReader buffreader = new BufferedReader(filereader);
    String s;

    while ((s = buffreader.readLine()) != null) {

        String[] tab = s.split("   ");
        double number = parseDouble(tab[0]);
        double lambda = parseDouble(tab[1]);
        double re = parseDouble(tab[2]);
        double im = parseDouble(tab[3]);

    }

}

private double parseDouble(String s) {
    if (s == null || s.isEmpty()) {
        return 0.0;
    } else {
        return Double.parseDouble(s);
    }
}

And when I'm trying to use lambda value (to add it to my ArrayList):

mylist.add(lambda);

I get an exception in line where lambda is declared:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1

What am I doing wrong?

Answer 1

If you want to split a string by any whitespace, like space or tab, a better way to do it is:

myString.split("\\s+");

In your example, the whitespaces among columns could be spaces, tabs, or mixture of both. String[] tab = s.split(" "); could results in only one element in variable tab. In this case, when you try to access the second element, you will get OutOfIndex error cause there is only one element in tab.

Answer 2

It might be because of formatting, but your data is separated by 5 spaces, you are splitting by 3 spaces. To avoid cases like that, it might make sense to use tabs or a regex like " {5}", stating the actual number of spaces instead of typing it manually.

Array out of bounds exception

2 个答案: