比较2个对象，错误的equals（）和hashcode？

Question

有人可以告诉我为什么它会回归＆＃34;不等于＆＃34;？我很长时间没有搜索这个...我认为我的哈希码或/和equals方法存在问题。

public class Main {
    public static void main(String[] args) {
        Student s1 = new Student();
        s1.setFirstName("Kamil");
        s1.setLastName("Witam");
        s1.setMark(3.0);
        s1.setAge(12);

        Student s2 = new Student();
        s2.setFirstName("Kamil");
        s2.setLastName("Witam");
        s2.setMark(3.0);
        s2.setAge(12);

        if( s1.equals(s2)){
            System.out.println("równe");
        }
        else{
            System.out.println("sraka");
        }
    }
}

我的hashCode：

public int hashCode()
{
    final int prime = 31;
    int result = 1;

    result = prime * result + age;
    result = prime * result + ( ( firstName == null ) ? 0 : firstName.hashCode() );
    result = prime * result + ( ( lastName == null ) ? 0 : lastName.hashCode() );

    long temp;
    temp = Double.doubleToLongBits( mark );
    result = prime * result + (int) ( temp ^ ( temp >>> 32 ) );

    return result;
}

等于：

public boolean equals( Object obj )
{
    if ( this == obj )
        return true;

    if ( obj == null )
        return false;

    if ( getClass() != obj.getClass() )
        return false;

    Student other = (Student) obj;

    if ( age != other.age )
        return false;

    if ( firstName == null )
    {
        if ( other.firstName != null )
            return false;
    }
    else 
        if ( !firstName.equals( other.firstName ) )
            return false;

    if ( lastName == null )
    {
        if ( other.lastName != null )
            return false;
    }
    else 
        if ( !lastName.equals( other.lastName ) )
            return false;

    if ( mark != other.mark )
        return false;

    return true;
}

有人可以向我解释一下：/？感谢