Error when collecting IntStream to map

Question

The following code

String[] values = ...
.... 
Map map = new HashMap<>();
for (int i = 0; i < values.length; i++) {
    map.pu         


        

Answer 1

Not very certain about how intelliJ's suggestion would work there, it seems inconsistent. Just put a

System.out.print(map);

statement between the declaration and loop and then it won't suggest you Replace with collect any further.

---

While using the IntStream#collect, the compilation fails for the reason that implementation of collect method expects three specified arguments as visible in the error as well while the

Collectors.toMap(i -> "X" + i, i -> values[i])

would result in only a single argument of type Collector.

---

Better way to convert the expression would be though to

• either use forEach

  Map map;
  IntStream.range(0, values.length).forEach(i -> map.put("X" + i, values[i]));
  

• Or use boxed() to convert the IntStream to Stream as:-

  Map map = IntStream.range(0, values.length).boxed()
             .collect(Collectors.toMap(i -> "X" + i, i -> values[i], (a, b) -> b));
  

• Or as suggested by @Holger, you can avoid using forEach and boxing overhead and modify the construct to make use of the IntStream.collect three-arg variant as:-

  Map map = IntStream.range(0, values.length)
             .collect(HashMap::new, (m,i) -> m.put("X"+i,values[i]), Map::putAll);