一、需求：创建一个HashMap集合，键是学号(String)，值是学生对象(Student),存储三个键值对元素，并遍历
分析：
HashMap集合对象public class StudentDemo {
public static void main(String[] args) {
//创建Map集合对象
Map<String,Student> m=new HashMap<String,Student>();
//添加键值对
m.put("01",new Student("张三"));
m.put("04",new Student("赵六"));
m.put("02",new Student("李四"));
m.put("03",new Student("王五"));
//遍历集合
Set<Map.Entry<String,Student>> s= m.entrySet();
//遍历
for (Map.Entry<String,Student> ss:s){
//根据键值对对象获取值和key
String key=ss.getKey();
Student value=ss.getValue();
System.out.println(key+","+value.getName());
}
System.out.println("------------------------");
//方式二，通过键找值
Set<String> m1=m.keySet();
for (String key :m1){
Student student =m.get(key);
System.out.println(key+","+student.getName());
}
}
}二、需求：创建一个HashMap集合，键是学生对象（Student)，值是地址(String),存储三个键值对元素，并遍历分析：
HashMap集合对象hashCode及equals方法public class StudentDemo {
public static void main(String[] args) {
//创建集合对象
Map<Student,String> m=new HashMap<Student,String>();
//添加键值对
m.put(new Student("张三",18),"上海");
m.put(new Student("李四",19),"北京");
m.put(new Student("王五",20),"上海");
m.put(new Student("王五",20),"海南");
//方式一
//获取所有键值对的集合
Set<Map.Entry<Student,String>> s=m.entrySet();
//方式一、遍历
for (Map.Entry<Student,String> mm:s){
//通过键值对获取对应的值与键
Student key=mm.getKey();
String value=mm.getValue();
System.out.println(key.getName()+","+key.getAge()+value);
}
System.out.println("---------------------------------");
//方式二
Set<Student> key=m.keySet();
for (Student s1:key){
String value=m.get(s1);
System.out.println(s1.getName()+","+s1.getAge()+","+value);
}
}
}
