'Concatenate a String to all elements of a Java stream

I have the following code that parses a Spliterator<Map.Entry> to a Map:

Spliterator<Map.Entry<String, String>> spliterator = ///;

Map<String, String> myMap = (StreamSupport
  .stream(spliterator, false)
  .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue)));

I want to change the code such as in my myMap, every key is concatenated with a constant String. Something like that :

Spliterator<Map.Entry<String, String>> spliterator = ///;
String myString = "hello";
String separator = "_";

Map<String, String> myMap = (StreamSupport
  .stream(spliterator, false)
  .collect(Collectors.toMap(myString+separator+Map.Entry::getKey, Map.Entry::getValue)));

I understand why this is not working but I don't find the good way to do that (without iterating over myMap after the stream). I am not familiar with Streams in Java so I probably missed something obvious.

javajava-stream


Solution 1:[1]

You can't use myString+separator+Map.Entry::getKey because Map.Entry::getKey is not a string but a method reference. You should instead use a lambda:

entry -> myString + separator + entry.getKey()

Solution 2:[2]

Use an explicit lambda function instead of a method reference:

.collect(toMap(
    e -> myString + separator + e.getKey(),
    Map.Entry::getValue
))

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Klitos Kyriacou
Solution 2 chrylis -cautiouslyoptimistic-

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