Hashメモリオーバーフローの問題

public class Student {
	
	public Student(int id, String name) {
		this.id = id;
		this.name = name;
	}

	private int id;
	
	private String name;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

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

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + id;
		result = prime * result + ((name == null) ? 0 : name.hashCode());
		return result;
	}

	@Override
	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 (id != other.id)
			return false;
		if (name == null) {
			if (other.name != null)
				return false;
		} else if (!name.equals(other.name))
			return false;
		return true;
	}
	
	
}

import java.util.HashSet;
import java.util.Set;

public class HashTest1 {

	public static void main(String[] args) {
		
		Set<Student> set = new HashSet<Student>();
		Student s1 = new Student(1,"jzk");
		Student s2 = new Student(2,"wyq");
		Student s3 = new Student(3,"jd");
		set.add(s1);
		set.add(s2);
		set.add(s3);
		
		System.out.println(set.size());
		s1.setName("jzk1");
		set.remove(s1);
		
		System.out.println(set.size());
		
	}

}