Collectors#toList(), toSet(), toMap()

Collector classを生成する
toList() streamの各要素としたListをreturnするCollectorを生成
toSet() streamの各要素としたSetをreturnするCollectorを生成
toMap() streamの各要素をFunctionで加工したkey, mapをMapとしてreturnするCollectorを生成

class Value {
    int price;
    String name;

    public Value(int price, String name) {
        this.price = price;
        this.name = name;
    }

    public int getPrice() {
        return price;
    }

    public void setPrice(int price) {
        this.price = price;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
    public String toString() {
        return "price:" + price + " name:" + name;
    }
}
public class Outer {
    public static void main(String[] args) {
        List<Value> l = Arrays.asList(
                new Value(1,"andy"),
                new Value(2,"john"),
                new Value(3,"laula"),
                new Value(4,"miki"),
                new Value(5,"sally"));
        Stream<Value> st = l.stream();
        List<Value> l2 = st.collect(Collectors.toList());
        l2.forEach(System.out::println);
        System.out.println("----------------------------");
        st = l.stream();
        Set<Value> s = st.collect(Collectors.toSet());
        s.forEach(System.out::println);
        System.out.println("----------------------------");
        st = l.stream();
        Map<String, Value> mp = st.collect(Collectors.toMap(
                Value::getName,
                b -> b));
        mp.keySet().stream().forEach(System.out::println);
        mp.keySet().stream().forEach(a -> System.out.println(mp.get(a)));
    }
}

price:1 name:andy
price:2 name:john
price:3 name:laula
price:4 name:miki
price:5 name:sally
----------------------------
price:3 name:laula
price:1 name:andy
price:2 name:john
price:4 name:miki
price:5 name:sally
----------------------------
miki
sally
john
laula
andy
price:4 name:miki
price:5 name:sally
price:2 name:john
price:3 name:laula
price:1 name:andy