传递参数化构造函数作为方法引用

Question

Is it possible to pass parameterized constructor as method reference to map ?

I've got a facility in my code that looks like this

items.stream()
        .map(it -> new LightItem(item.getId(), item.getName())
        .collect(Collectors.toList());

My items list constains several Item objects

Item
   id, name, reference, key...

whereas LightItem has only two fields

LightItem
    id, name

It would be good if it was possible to do something like this

items.stream().map(LightItem::new).collect(Collectors.toList())

Answer 1

There's only one way to use constructor here, you have to add a new constructor to LightItem class:

public LightItem(Item item) {
    this.id = item.getId();
    this.name = item.getName();
}

This will allow you to use the code you wrote:

items.stream().map(LightItem::new).collect(Collectors.toList())

If you really don't want to add a new constructor to LightItem , there's way around:

class MyClass {

    public List<LightItem> someMethod() {
        return items.stream()
            .map(MyClass::buildLightItem)
            .collect(Collectors.toList());
    }

    private static LightItem buildLightItem(Item item) {
        return new LightItem(item.getId(), item.getName());
    }

}