HashMap

 //需求：创建一个HashMap集合，键是学生对象Student，值是籍贯，储存3个键值对对象并遍历，要求同性别，同年龄位同一个学生
        //核心点：如果是键存储自定义对象，需要重写equal和Hashcode方法
        //创建一个map集合
        HashMap<Student,String> hashMap=new HashMap<>();
        //创建对象
        Student student1 = new Student("张三", "25");
        Student student2= new Student("李四", "35");
        Student student3 = new Student("王五", "45");
        //添加元素
        hashMap.put(student1,"江西");
        hashMap.put(student2,"万年");
        hashMap.put(student3,"苏桥");
        //键值对遍历
        Set<Map.Entry<Student, String>> entries = hashMap.entrySet();
        for (Map.Entry<Student, String> entry : entries) {
            Student key = entry.getKey();
            String value = entry.getValue();
            System.out.println(key+value);
        }
        System.out.println("-------------------------------------------------------------");
        //键遍历
        Set<Student> students = hashMap.keySet();
        for (Student key : students) {
            String value = hashMap.get(key);
            System.out.println(value+key);
        }
        System.out.println("-------------------------------------------------------------");
        //lambda表达式遍历
        hashMap.forEach(new BiConsumer<Student, String>() {
            @Override
            public void accept(Student student, String s) {
                System.out.println(student+s);
            }
        });


    }
}
class Student{
    private String name;
    private String age;

    public Student() {
    }

    public Student(String name, String age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }
    //关于值，重写方法

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Student student = (Student) o;
        return Objects.equals(name, student.name) &&
                Objects.equals(age, student.age);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name, age);
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age='" + age + '\'' +
                '}';
    }
}