HashTable.java

import java.util.ArrayList;
import java.util.List;
import java.util.Vector;

public class HashTable
{
    private final int numberOfBuckets = 50;
    private final Vector<List<HashTableNode>> buckets;
    
    private class HashTableNode
    {
        private String key;
        private String value;
        
        public HashTableNode(String key, String value)
        {
            this.key = key;
            this.value = value;            
        }
        
        public String getKey()
        {
            return key;
        }

        public String getValue()
        {
            return value;
        }
    }
    
    public HashTable()
    {
        buckets = new Vector<>();
        buckets.ensureCapacity(50);
    }
    
    public void add(String key, String value)
    {
        int hash = hash(key);
        List<HashTableNode> bucket = buckets.elementAt(hash); 
        if (bucket == null)
        {
            bucket = new ArrayList<>(); 
            buckets.add(hash, bucket);
        }
        bucket.add(new HashTableNode(key, value));
    }
    
    public String get(String key)
    {
        int hash = hash(key);
        List<HashTableNode> bucket = buckets.elementAt(hash);
        if (bucket == null)
        {
            return null;
        }
        
        for (HashTableNode node : bucket)
        {
            if (node.getKey().equals(key))
            {
                return node.getValue();
            }
        }
        
        return null;
    }

    private int hash(String value)
    {
        return value.charAt(0) % numberOfBuckets;        
    }
}