Java8与Collectors.toMap的连接映射

public static <T, K, U> Collector<T, ?, Map<K,U>> toMap(Function<? super T, ? extends K> keyMapper,
                                                      Function<? super T, ? extends U> valueMapper)

import java.util.*;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args) {
        List<String> names = Arrays.asList("Alice", "Bob", "Charlie", "Dave");

        Map<String, Integer> nameLengths = names.stream()
                .collect(Collectors.toMap(
                        name -> name,
                        name -> name.length()
                ));

        System.out.println(nameLengths);
    }
}

{Alice=5, Bob=3, Charlie=7, Dave=4}