File size: 1,817 Bytes
0284885 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | package HashMap_package1;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.function.BiConsumer;
public class HashMap_demo {
public static void main(String[] args) {
/*
需求：创建一个HashMap集合，键是学生对象(Student)，值是籍贯(String)。
存储三个键值对元素，并遍历
要求：同姓名，同年龄认为是同一个学生
核心点：
HashMap的键位置如果存储的是自定义对象，需要重写hashCode和equals方法。
*/
//1、创建HashMap的对象
HashMap<Student, String> hm = new HashMap<>();
//2、创建三个学生对象
Student s1 = new Student("zhangsan", 23);
Student s2 = new Student("lisi", 24);
Student s3 = new Student("wangwu", 25);
//3、添加元素
hm.put(s1, "江苏");
hm.put(s2, "浙江");
hm.put(s3, "福建");
//4、遍历集合
Set<Student> keys = hm.keySet();
for (Student key : keys) {
String value = hm.get(key);
System.out.println(key + "=" + value);
}
System.out.println("----------------------------------------");
Set<Map.Entry<Student, String>> entries = hm.entrySet();
for (Map.Entry<Student, String> entry : entries) {
Student key = entry.getKey();
String value = entry.getValue();
System.out.println(key + "=" + value);
}
System.out.println("----------------------------------------");
hm.forEach(new BiConsumer<Student, String>() {
@Override
public void accept(Student key, String value) {
System.out.println(key + "=" + value);
}
});
}
}
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