Is there a way in Java to do something like:
int foo[] = new int[0..n];
i.e
foo[0] = 0
foo[3] = 3
1
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Unfortunately not :'( Look at this: stackoverflow.com/questions/2950386/…Lews Therin– Lews Therin2012-10-18 22:36:14 +00:00Commented Oct 18, 2012 at 22:36
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3 Answers
Not using built-in language features. You can easily write a method to do it, of course, but there's nothing built-in - and I suspect that it's sufficiently rarely useful that it's not in many third party utility libraries (such as Guava) either.
1 Comment
Louis Wasserman
The closest Guava-based alternative is
Range.closed(0, 3).asSet(DiscreteDomains.integers()).asList(). That's a mouthful, but that's because you really ought to just do it yourself.I don't think so, but you could use a simple for-loop:
int foo[n];
for(int i = 0; i < n; i++) foo[i] = i;
And if you want a method try something like this:
public void initialize(int[] array, int start, int end) {
int array_length = array.length;
if (end > array_length) end = array_length;
for (int i = start; i < end; i++) {
array[i - start] = i;
}
}
// In any other point in your code
int foo[] = new int[6];
initialize(foo, 0, 10);
Another way would be to make a Range class to add this functionality:
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
public class Range implements Iterable<Integer> {
Integer array[];
public Range(int size) {
this(0, size - 1);
}
public Range(int start, int end) {
array = new Integer[end - start];
for (int i = start; i < end; i++) {
array[i - start] = i;
}
}
public List<Integer> asList() {
return Arrays.asList(array);
}
@Override
public Iterator<Integer> iterator() {
return Arrays.asList(array).iterator();
}
}
Here is an usage example:
Range range = new Range(4, 10);
for (int i : range) {
System.out.println(i);
}
I'm sure that this code can be improved but it isn't worth it.
answered Oct 18, 2012 at 22:36
David Moreno García
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2 Comments
ruakh
+1, but that probably should be
[n+1] and i <= n. At least, I'd expect that a notation like the OP's new int[0..n] would include both endpoints, 0 and n.
David Moreno García
Yes, you are right, but would be easier to declare n as n+1 xD Anyway, is a simple example to say that what he is looking for is not possible. Thanks for your comment anyway ;)
int n = 10;
int[] arr = new int[n+1];
for loops has flexible syntax, so you can do even this:
for ( int i = 0; i < arr.length; arr[i] = i++ );
P.S.
If you want less code than above, you can do this:
int i = 0;
for ( int c : arr ) { arr[i] = i++; }
P.P.S.
Despite the fact that these pieces of code are laconic, for me they seems unclear, and smells bad.
