Is There a Java Equivalent of Python's 'Enumerate' Function?

Question

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?

Accepted Answer

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

Answer 2

I find this to be the most similar to the python approach.

Must Read

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);
    }
}

Is There a Java Equivalent of Python's 'Enumerate' Function?

11 Answers

Must Read

Usage

Elena Rostova