set集合概述：

1，set集合是一个不包含重复数据的Collection

2，set集合中的数据是无序的(因为set集合没有下标)

3，set集合中的元素不可以重复--常用来给数据去重复

4，set集合可以存储null值，最多存储一个

5，set集合去除重复的时候(泛型如果自己定义的类型的时候)你需要在自己定义的类中重写hashCode()方法和equals()方法

测试代码如下：自定义一个Student类，然后创建一个set集合对象，将创建的Student对象s1,s11,s2放入到set集合对象中

package cn.tedu.map;
import java.util.Objects;
public class Student {
    private String name;
    private int age;
    private String tel;

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

    public String getName() {
        return name;
    }

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

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getTel() {
        return tel;
    }

    public void setTel(String tel) {
        this.tel = tel;
    }

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

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

public class TestSet {
    public static void main(String[] args) {
        Set<String> set=new HashSet<>();
        Set<Student> student = new HashSet<>();
        Student s=new Student("张三",3,"3333");
        Student s1=new Student("张三",3,"3333");
        Student s2=new Student("李四",4,"4444");
        student.add(s);
        student.add(s1);
        student.add(s2);
        System.out.println(student);
    }
}

最后打印的结果：
[Student{name='李四', age=4, tel='4444'}, Student{name='张三', age=3, tel='3333'}]