HashSet中存放不重复元素

一.自定义对象存放在hashSet中，保证元素不重复。重写hashCode()和equals()方法

public class Student{

    private String name;

    private Integer age;

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

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

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

    @Override
    public int hashCode() {
        //return name.hashCode()+age;
        //为了让hash值的范围大一些,我们这里可以乘以一个常数
        return name.hashCode()+age*39;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj){
            //如果是同一个引用,不用比较了
            return true;
        }
        if (!(obj instanceof Person)){
            //如果类型不能转换,不用比较了
            throw new ClassCastException("类型错误");
        }
        Student student = (Student) obj;
        return this.name.equals(student.name) && this.age == student.age;
    }
}