\u539f\u6587\u94fe\u63a5\uff1ahttps:\/\/www.jb51.net\/article\/149605.htm<\/p>\n
1.for\u5faa\u73af<\/p>\n
\r\n<pre class="brush:java;">import com.google.common.base.Function;\r\nimport com.google.common.collect.Maps;\r\nimport java.util.ArrayList;\r\nimport java.util.HashMap;\r\nimport java.util.List;\r\nimport java.util.Map;\r\npublic class ListToMap {\r\n public static void main(String[] args) {\r\n List<User> userList = new ArrayList<>();\r\n User user1 = new User();\r\n user1.setId(1L);\r\n user1.setAge("12");\r\n User user2 = new User();\r\n user2.setId(2L);\r\n user2.setAge("13");\r\n userList.add(user1);\r\n userList.add(user2);\r\n Map<Long, User> maps = new HashMap<>();\r\n for (User user : userList) {\r\n maps.put(user.getId(), user);\r\n }\r\n System.out.println(maps);\r\n }\r\n public static class User {\r\n private Long id;\r\n private String age;\r\n public Long getId() {\r\n return id;\r\n }\r\n public void setId(Long id) {\r\n this.id = id;\r\n }\r\n public String getAge() {\r\n return age;\r\n }\r\n public void setAge(String age) {\r\n this.age = age;\r\n }\r\n @Override\r\n public String toString() {\r\n return "User{" +\r\n "id=" + id +\r\n ", age='" + age + '\\'' +\r\n '}';\r\n }\r\n }\r\n}<\/pre>\r\n<\/pre>\n2.\u4f7f\u7528guava<\/p>\n
\r\n<pre class="brush:java;">Map<Long, User> maps = Maps.uniqueIndex(userList, new Function<User, Long>() {\r\n @Override\r\n public Long apply(User user) {\r\n return user.getId();\r\n }\r\n});\r\n<\/pre>\n3.\u4f7f\u7528JDK1.8 lambda\u8868\u8fbe\u5f0f<\/strong><\/p>\n\r\n<div class="jb51code">\r\n<pre class="brush:java;">Map<Long, User> maps = userList.stream().collect(Collectors.toMap(User::getId, user -> user));<\/pre>\r\n<\/div>\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"