I have the below code to implement the requirement, but couldn't solve using stream , I'm not sure how to increment i in pipeline
String[] str = {"a","b","c","d","e","f"}; Map<String, String> strMap = new HashMap<>(); int i = 0; while(i< str.length && i +1 < str.length) { strMap.put(str[i],str[i+1]); i +=2; } You can't do it with a simple stream of str, but you can mimic your loop with an index stream:
Map<String, String> strMap = IntStream.range(0, str.length - 1) .filter(i -> i % 2 == 0) .boxed() .collect(Collectors.toMap(i -> str[i], i -> str[i + 1])); 
It's a bit of a hack, but you could use an IntStream to generate your indices (between 0 and the length of the array), filter out the odd indices and then use a forEach to populate the strMap - like,
String[] str = { "a", "b", "c", "d", "e", "f" }; Map<String, String> strMap = new HashMap<>(); IntStream.range(0, str.length).filter(i -> i % 2 == 0) .forEach(i -> strMap.put(str[i], str[i + 1])); System.out.println(strMap); Which outputs (as requested)
{a=b, c=d, e=f} 
IntStream.range(0, str.length/2).map(i -> i*2) which performs less operations, but on the other hand, won’t fail-fast when the array has an odd length.
i< str.length && i +1 < str.lengthis redundant.