In Python, the enumerate function allows you to iterate over a sequence of (index, value) pairs. For example:
>>> numbers = ["zero", "one", "two"]
>>> for i, s in enumerate(numbers):
... print i, s
...
0 zero
1 one
2 two
Is there any way of doing this in Java?
11 Answers
For collections that implement the List interface, you can call the listIterator() method to get a ListIterator. The iterator has (amongst others) two methods - nextIndex(), to get the index; and next(), to get the value (like other iterators).
So a Java equivalent of the Python above might be:
import java.util.ListIterator;
import java.util.List;
List<String> numbers = Arrays.asList("zero", "one", "two");
ListIterator<String> it = numbers.listIterator();
while (it.hasNext()) {
System.out.println(it.nextIndex() + " " + it.next());
}
which, like the Python, outputs:
0 zero
1 one
2 two
I find this to be the most similar to the python approach.
Usage
public static void main(String [] args) {
List<String> strings = Arrays.asList("zero", "one", "two");
for(EnumeratedItem<String> stringItem : ListUtils.enumerate(strings)) {
System.out.println(stringItem.index + " " + stringItem.item);
}
System.out.println();
for(EnumeratedItem<String> stringItem : ListUtils.enumerate(strings, 3)) {
System.out.println(stringItem.index + " " + stringItem.item);
}
}
