StringTokenizer“ NoExploranceException”

Question

So For some reason i'm getting a java.lang.Exception: java.util.NoSuchElementException. The values are priting off like this.

back
bison
1.0
back
dog
3.0
becaue
bison
1.0
best
bison
1.0
david
bison
1.0
ever
bison
1.0
i
bison
1.0
i
dog
4.0
im
bison
1.0
is
bison
1.0

But at the very end i get the NoSuchelementException:

my code is simple:

StringTokenizer line = new StringTokenizer(new String(value.getBytes()));
    while (line.hasMoreElements()){
        Text unWord = new Text((String) line.nextElement());
        String unAuth = (String) line.nextElement();
        float unVal = Float.parseFloat(line.nextToken());

        System.out.println(unWord);
        System.out.println(unAuth);
        System.out.println(unVal);
    }

I can't seem to figure out why the Elements would print off, but i would get a noSuchelementException at the end.

Answer 1

The problem is that you call hasMoreElements() once per iteration, but you call nextElement / nextToken three times. This is error-prone. Even if the file follows the exact format, such as in your case, there is a possibility of having a blank line at the end.

It looks like that is precisely what is happening in your case: when you ask if the tokenizer has more elements, you get true , but there is only one element, which happens to be a new line character. The first call to nextElement succeeds, but the second one fails.

To fix this problem add hasMoreElements() check before each call to nextElement , and quit if there is no next element:

Text unWord = new Text((String) line.nextElement());
if (!line.hasMoreElements()) break;
String unAuth = (String) line.nextElement();
if (!line.hasMoreElements()) break;
float unVal = Float.parseFloat(line.nextToken());

Answer 2

Well you call line.nextElement() twice while only checking for line.hasMoreElements() once. Could it be that there's only one remaining element at the end, not two?

Answer 3

On each iteration of your loop, you test once whether there are any more tokens available, and then attempt to draw three tokens from the tokenizer. You print the results if all three tokens are successfully drawn, but you can be confident only of one being successfully drawn. If the total number of tokens in the original string is not a multiple of three then you will certainly get a NoSuchElementException . If you think your data otherwise look as you expect, then that might result from trailing whitespace in your original string (yielding an unexpected empty token at the end).