I have two lists I want to compare each element of list 1 to list 2 and get result in list 3 e.g
List1 = {99,22,33}
list2 = {11,24,33}
Result:
list3 = {1,-1,0}
How I can do this preferably using stream?
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1Are lists guaranteed to have same size? If not how would you like such situation to be handled?Pshemo– Pshemo2020-04-04 21:19:47 +00:00Commented Apr 4, 2020 at 21:19
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1 Answer
Try it like this:
This replaces the stream of ints used to index each list, with the result of the comparison. Then collect those into a list.
Note: I added a safeguard to account for different size lists. It will use the smaller of the two to prevent an exception being thrown. But trailing elements of the longer list will be ignored.
List<Integer> list1 = List.of(99, 22, 33);
List<Integer> list2 = List.of(11, 24, 33);
// safeguard against different sized lists.
int minLen = Math.min(list1.size(), list2.size());
List<Integer> result = IntStream.range(0, minLen)
.map(i -> list1.get(i).compareTo(list2.get(i)))
.boxed().collect(Collectors.toList());
System.out.println(result);
Prints
[1, -1, 0]
5 Comments
Lkopo
Nice solution but as @Pshemo said, it will work only when both list will have the same size. If list2 will have less members, a runtime exception will be thrown. Anyway, OP mentioned Java 8, so
List.of are part of the Java 9, therefore I'd change it to Arrays.asList :)
WJS
Yeah. I amended my answer and used Math.min() to get the minimum length to avoid an exception. It is up to the OP if they want it or not.
Sonali
Yes both list will be of same size. Thanks for solution this will work for me @WJS
Naman
or use
mapToObj instead of the map...boxed combinationNaman
@WJS It is indeed strange. A recent survey collected feedback and similar comments were marked by me over it. I believe the site somehow lacks to refrain the "rich from becoming richer". (no further discussion here about it though)