What are the lazy and eager operators?
When studying the Stream API, I often encountered the use of the expressions lazy and eager operators, but I could not really find a normal definition of these concepts anywhere.
Can someone explain clearly?
1 answers
In programming terms:
- Lazy evaluation means that calculations are performed only when the result is needed.
- Eager evaluation - means that calculations are performed strictly on request.
For example, let's say you sort the array int arr[] - the operation is quite computationally expensive.
Traditionally, it is customary to choose the eager approach, call the array sorting: Arrays.sort(arr), then use the result.
In the case of lazy - the array is not sorted in advance, but we sort only at the moment when we need arr[i] - a certain element of the sorted array - and only then we call sorting-do you feel the difference?
In the Stream API, almost all operations are lazy, intermediate calculations are performed only when calling terminal operations of the type reduce()/count()/collect() , etc.