- HashMap存储自定义类型键值
- Map集合保证key是唯一的：作为key的元素，必须重写hashCode方法和equals方法，以保证key唯一
package collection;import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
import java.util.Set;public class Demo01HashMapSavePerson {public static void main(String[] args) {show01();System.out.println("==================");show02();}private static void show02() {HashMap<Person, String> map = new HashMap<>();map.put(new Person("女王", 18), "英国");map.put(new Person("秦始皇", 18), "泰国");map.put(new Person("普京", 30), "俄罗斯");map.put(new Person("女王", 18), "毛里求斯");Set<Map.Entry<Person, String>> set = map.entrySet();for (Map.Entry<Person, String> entry : set) {Person key = entry.getKey();String value = entry.getValue();System.out.println(key + "-->" + value);}}private static void show01() {HashMap<String, Person> map = new HashMap<>();map.put("北京", new Person("张三", 18));map.put("广州", new Person("李四", 19));map.put("广东", new Person("王五", 20));map.put("北京", new Person("赵六", 21));Set<String> set = map.keySet();for (String key : set) {Person value = map.get(key);System.out.println(key + "-->" + value);}}
}class Person {private String name;private int age;public Person() {}public Person(String name, int age) {this.name = name;this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}@Overridepublic boolean equals(Object object) {if (this == object) return true;if (object == null || getClass() != object.getClass()) return false;Person person = (Person) object;return age == person.age && Objects.equals(name, person.name);}@Overridepublic int hashCode() {return Objects.hash(name, age);}@Overridepublic String toString() {return "Person{" +"name='" + name + '\'' +", age=" + age +'}';}
}
D:\Java\jdk-17\bin\java.exe "-javaagent:D:\BaiduNetdiskDownload\IntelliJ IDEA 2023.2\lib\idea_rt.jar=13388:D:\BaiduNetdiskDownload\IntelliJ IDEA 2023.2\bin" -Dfile.encoding=UTF-8 -classpath F:\IdeaProjects\JavaSenior\out\production\Test;D:\develop\maven\repository\junit\junit\4.13.1\junit-4.13.1.jar;D:\develop\maven\repository\org\hamcrest\hamcrest-core\1.3\hamcrest-core-1.3.jar collection.Demo01HashMapSavePerson
广州-->Person{name='李四', age=19}
广东-->Person{name='王五', age=20}
北京-->Person{name='赵六', age=21}
==================
Person{name='女王', age=18}-->毛里求斯
Person{name='秦始皇', age=18}-->泰国
Person{name='普京', age=30}-->俄罗斯Process finished with exit code 0
1、HashMap集合的特点
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)
