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Is there a way to get an element id of a list to get it later through list.get(index)
when using
for(Object obj: o)
construction
Only define a local var and manually incrementing it? Anything simpler?
557
Use List Comprehension and the enumerate() Function to Get the Indices of All Occurrences of an Item in A List.
indexOf() in Java. The indexOf() method of ArrayList returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element. Syntax : public int IndexOf(Object o) obj : The element to search for.
The get() method of ArrayList in Java is used to get the element of a specified index within the list. Parameter: Index of the elements to be returned. It is of data-type int. Return Type: The element at the specified index in the given list.
The index of a particular element in an ArrayList can be obtained by using the method java. util. ArrayList. indexOf().
No, for-each loop doesn't keep track of index. You can either use a regular indexed loop, or do something like this:
int idx = 0;
for (Object o : list) {
...
idx++;
}
This is risky since break/continue will make idx goes out of sync, so do use this infrequently, and only when the body is simple and only a few lines long.
If the elements are distinct, List.indexOf would also work, albeit at O(N), and at that point you may want to consider a Set (unordered, but guaranteed distinct).
It should also be said that sometimes using a listIterator() also alleviates the need of an explicit index while iterating.
A ListIterator supports add, set and remove operations.
This is another clear advantage List has over arrays as far as iteration mechanism goes.
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