Java 8 List<V> into Map<K, V>

Question

I want to translate a List of objects into a Map using Java 8's streams and lambdas.

This is how I would write it in Java 7 and below.

private Map<String, Choice> nameMap(List<Choice> choices) {         final Map<String, Choice> hashMap = new HashMap<>();         for (final Choice choice : choices) {             hashMap.put(choice.getName(), choice);         }         return hashMap; } 

I can accomplish this easily using Java 8 and Guava but I would like to know how to do this without Guava.

In Guava:

private Map<String, Choice> nameMap(List<Choice> choices) {     return Maps.uniqueIndex(choices, new Function<Choice, String>() {          @Override         public String apply(final Choice input) {             return input.getName();         }     }); } 

And Guava with Java 8 lambdas.

private Map<String, Choice> nameMap(List<Choice> choices) {     return Maps.uniqueIndex(choices, Choice::getName); } 

Answer 1

Based on Collectors documentation it's as simple as:

Map<String, Choice> result =     choices.stream().collect(Collectors.toMap(Choice::getName,                                               Function.identity()));