How do i convert string array into long array in java?

[Birla Murugesan]

How do i convert string array into long array in java?

what i am having is:

String [] users = emailsorusers.split(",");

i want to convert this into Long Arrays

please help in this regards.

Thanks in advance,
Birla

[Jesper Young]

So the String array users now contains strings that contain all digits? You'll need to create a Long array of the same length as the String array and then iterate through the String array to fill the elements of the Long array:

Long[] data = new Long[users.length];
for (int i = 0; i < users.length; i++) {
  data[i] = Long.valueOf(users[i]);
}

[Birla Murugesan]

Without iterating the array,Is there is any other way to do it.

[Rob Prime]

Simply put, no. Whatever solution you use, in the end you will still need to change each separate string element into a long.

Jesper, I'd suggest one slight modification: use long instead of Long:

long[] data = new long[users.length];   
for (int i = 0; i < users.length; i++) {   
    data[i] = long.parseLong(users[i]);   
}  

[Henry Wong]

Birla Murugesan wrote:
Without iterating the array,Is there is any other way to do it.

Rob Prime wrote:Simply put, no. Whatever solution you use, in the end you will still need to change each separate string element into a long.

A more complicated answer ... Maybe. You already iterated once through the string, in order to split it into an array. Technically, there is a way to do without iterating through the array -- you can skip generating the array in the first place.

Instead of using split(), you can use find(), to get each "long" string element, in order to convert to a long -- in one pass.

Now, of course, whether this saves any time, is unclear.

Henry

[Rob Prime]

Henry Wong wrote:

Birla Murugesan wrote:
Without iterating the array,Is there is any other way to do it.

Rob Prime wrote:Simply put, no. Whatever solution you use, in the end you will still need to change each separate string element into a long.

A more complicated answer ... Maybe. You already iterated once through the string, in order to split it into an array. Technically, there is a way to do without iterating through the array -- you can skip generating the array in the first place.

Instead of using split(), you can use find(), to get each "long" string element, in order to convert to a long -- in one pass.

Now, of course, whether this saves any time, is unclear.

Henry

I agree that splitting and parsing in one go would remove the need for a second iteration. And I doubt that using a Pattern / Matcher combination would be slower - because that's just what String.split uses - it delegates to Pattern.split which uses a Matcher. This splitting a string into longs would be something like this (code based on Pattern.split):

Pattern pattern = Pattern.compile(",");
Matcher matcher = pattern.matcher(input);
List<Long> matches = new ArrayList<Long>();
int index = 0;
while (matcher.find())
{
    String match = input.substring(index, matcher.start());
    matches.add(Long.valueOf(match));
    index = matcher.end();
}
// add remainder
String match = input.substring(index);
matches.add(Long.valueOf(match);
// matches now contains all Longs found in the string

Of course that would require another iteration to turn the List<Long> into a Long[] or long[], but the List<Long> should be fine for most cases.

But the initial question was: "How do i convert string array into long array in java?" and that's impossible without a second iteration (I count recursion as iterating in this case).

[Jesper Young]

Rob Prime wrote:Jesper, I'd suggest one slight modification: use long instead of Long:

Ok, but the OP specifically asked for a Long array. This line of your modified version does not work:

data[i] = long.parseLong(users[i]);

It should be:

data[i] = Long.parseLong(users[i]);

[Rob Prime]

Jesper Young wrote:

Rob Prime wrote:Jesper, I'd suggest one slight modification: use long instead of Long:

Ok, but the OP specifically asked for a Long array.

Actually, the OP asked for both:

How do i convert string array into long array in java?

i want to convert this into Long Arrays

This line of your modified version does not work:

data[i] = long.parseLong(users[i]);

It should be:

data[i] = Long.parseLong(users[i]);

Guess my mental search-and-replace worked too good