Java8从对象列表中取出某个属性的列表

List<属性值类型> 属性List = 对象List.stream().map(对象::get方法()).collect(Collectors.toList());

例如：

List<Integer> idList = list.stream().map(User::getId).collect(Collectors.toList());

//或者
List<Integer> idList = list.stream().map(u -> u.getId()).collect(Collectors.toList());

举例

public class HelloWorld {

    public static void main(String[] args) {
        List<User> list = new ArrayList<>();
        for(int i=1;i<=10;i++) {
            User u = new User(i, "用户-" + i);
            list.add(u);
        }
        //取出id列表
        //List<Integer> idList = list.stream().map(User::getId).collect(Collectors.toList());
        List<Integer> idList = list.stream().map(u -> u.getId()).collect(Collectors.toList());

        System.out.println("id列表：" + idList);
    }
    private static class User{
        int id;
        String name;

        public User(int id, String name) {
            this.id = id;
            this.name = name;
        }

        public int getId() {
            return id;
        }

        public void setId(int id) {
            this.id = id;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        @Override
        public String toString() {
            return "User{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    '}';
        }
    }

}

执行后：