JDK8怎么通過(guò)Stream對(duì)List、Map操作和互轉(zhuǎn)

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1、Map數(shù)據(jù)轉(zhuǎn)換為自定義對(duì)象的List，例如把map的key,value分別對(duì)應(yīng)Person對(duì)象兩個(gè)屬性：

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());

以上三種方式不同之處在于排序的處理。參考鏈接：

https://www.concretepage.com/java/jdk-8/java-8-convert-map-to-list-using-collectors-tolist-example

2、List對(duì)象轉(zhuǎn)換為其他List對(duì)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、從List中過(guò)濾出一個(gè)元素

User match = users.stream().filter((user) -> user.getId() == 1).findAny().get();

4、List轉(zhuǎn)換為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));

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