1、Map数据转换为自定义对象的List，例如把map的key,value分别对应Person对象两个属性：
List<Person> list = map.entrySet().stream().sorted(Comparator.comparing(e -> e.getKey())) .map(e -> new Person(e.getKey(), e.getValue())).collect(Collectors.toList()); List<Person> list = map.entrySet().stream().sorted(Comparator.comparing(Map.Entry::getValue)) .map(e -> new Person(e.getKey(), e.getValue())).collect(Collectors.toList()); List<Person> list = map.entrySet().stream().sorted(Map.Entry.comparingByKey()) .map(e -> new Person(e.getKey(), e.getValue())).collect(Collectors.toList());
以上三种方式不同之处在于排序的处理。参考链接：
https://www.concretepage.com/java/jdk-8/java-8-convert-map-to-list-using-collectors-tolist-example
2、List对象转换为其他List对象：
List<Employee> employees = persons.stream()
.filter(p -> p.getLastName().equals("l1"))
.map(p -> new Employee(p.getName(), p.getLastName(), 1000))
.collect(Collectors.toList());
3、从List中过滤出一个元素
User match = users.stream().filter((user) -> user.getId() == 1).findAny().get();
4、List转换为Map
public class Hosting {
private int Id;
private String name;
private long websites;
public Hosting(int id, String name, long websites) {
Id = id;
this.name = name;
this.websites = websites;
}
//getters, setters and toString()
}
Map<Integer, String> result1 = list.stream().collect(
Collectors.toMap(Hosting::getId, Hosting::getName));
