import java.util.*; // for ArrayList, Collection, etc

class student implements Comparable<student>  // generic boring class
{
    public final String name;   // used as "key"
    public final int id;
    protected double gpa;
    protected String major;
    // ... other boring stuff skipped
    public student(String n, int i)
    {   name=n; id=i;
	gpa = ((int)(Math.random()*401))/100.0;
	major = "cs";
    }
    public String toString()
    {return name+" has id "+id+" and gpa "+gpa; }
    public int compareTo(student s) { return id -s.id; } //default compare
}//student

public class shash
{
    protected ArrayList<student>[] H;
    protected int size;
    public int size() { return size; }
    public shash(int buckets)
    {
	H = new ArrayList[buckets]; // expect compiler warning
    }
    protected int hash(String key)
    {
	int ax = 0; // accumulator
	for(int i=0;i<key.length();i++) ax += (int)key.charAt(i);
	return ax % H.length;
    }
    protected String getkey(student s) { return s.name; }

    // insert, lookup, delete

    // insert should also replace previous record for student with
    // new record
    public void insert(student s)
    {
	String key = getkey(s);
	int hi = hash(key);
	if (H[hi]==null) H[hi] = new ArrayList<student>();
	else if (H[hi].remove(s)) size--; // remove old record
	H[hi].add(s);
	size++;
    }

    protected student search(String key, boolean del)
    {
	student answer = null;
	if (key==null) return null;
	int hi = hash(key);
	for(student s:H[hi])
	    if (key.equals(getkey(s)))
		{
		    answer = s;
		    if (del) { H[hi].remove(s); size--; }
		    return answer; //break;
		}
        return answer;
    }
    public student lookup(String key) { return search(key,false); }
    public student delete(String key) { return search(key,true); }
    

    public static void main(String[] av)
    {
	shash HT = new shash(1000);
	HT.insert(new student("mary",702123456));
	HT.insert(new student("larz",701654321));
	HT.insert(new student("narx",702111111));
	HT.delete("larz");
	System.out.println( HT.lookup("mary"));
	System.out.println( HT.lookup("narx"));
	System.out.println( HT.lookup("larz"));		
    }
    
}//shash