Java 8中如何将List＜V＞转换为Map＜K, V＞呢?

List转Map的实现思路

1.for循环将List转换为Map
2.使用Guava的写法
3.借助java8中的Lambdas进行list和map的转换

Java 7

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;
}

Guava转换List为Map

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();
        }
    });
}

Guava +Java 8 lambdas将list转换为map

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

List<Item> list = new ArrayList<>();
list.add(new Item("code1", "java265.com-1"));
list.add(new Item("code2", "java265.com-2"));

Map<String,String> map = list.stream()
     .collect(Collectors.toMap(Item::getCode, Item::getName));