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Java三种方法将List转换为Map的实例

1.for循环

<pre class="brush:java;">import mon.base.Function;import mon.collect.Maps;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;public class ListToMap {public static void main(String[] args) {List<User> userList = new ArrayList<>();User user1 = new User();user1.setId(1L);user1.setAge("12");User user2 = new User();user2.setId(2L);user2.setAge("13");userList.add(user1);userList.add(user2);Map<Long, User> maps = new HashMap<>();for (User user : userList) {maps.put(user.getId(), user);}System.out.println(maps);}public static class User {private Long id;private String age;public Long getId() {return id;}public void setId(Long id) {this.id = id;}public String getAge() {return age;}public void setAge(String age) {this.age = age;}@Overridepublic String toString() {return "User{" +"id=" + id +", age='" + age + '\'' +'}';}}}</pre>

2.使用guava

<pre class="brush:java;">Map<Long, User> maps = Maps.uniqueIndex(userList, new Function<User, Long>() {@Overridepublic Long apply(User user) {return user.getId();}});

3.使用JDK1.8lambda表达式

<div class="jb51code"><pre class="brush:java;">Map<Long, User> maps = userList.stream().collect(Collectors.toMap(User::getId, user -> user));</pre></div>