Student类如下所示：

package com.test.Test07;import java.util.Objects;public class Student {private int age;private String name;public int getAge() {return age;}public void setAge(int age) {this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}@Overridepublic String toString() {return "Student{" +"age=" + age +", name='" + name + '\'' +'}';}public Student(int age, String name) {this.age = age;this.name = name;}@Overridepublic 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);}@Overridepublic int hashCode() {return Objects.hash(age, name);}
}

测试类如下所示：

package com.test.Test07;import java.util.HashSet;public class TestStudent {//这是一个main方法，是程序的入口public static void main(String[] args) {//创建一个HashSet集合HashSet<Student> hs = new HashSet<>();hs.add(new Student(19,"lili"));hs.add(new Student(20,"lulu"));hs.add(new Student(18,"feifei"));hs.add(new Student(19,"lili"));hs.add(new Student(10,"nana"));System.out.println(hs.size());  // 5System.out.println(hs);         //[Student{age=18, name='feifei'}, Student{age=10, name='nana'}, Student{age=20, name='lulu'}, Student{age=19, name='lili'}, Student{age=19, name='lili'}]/*//现在就变成了4条数据，HashSet符合唯一性的特点了。4[Student{age=18, name='feifei'}, Student{age=19, name='lili'}, Student{age=20, name='lulu'}, Student{age=10, name='nana'}]*/}
}