CareerCup

Implement two-level of hashing, two hash functions

h1( typename ) returns a key k1 in table T1 which contains links to a separate table T2(one T2 per entry of T1)
h2(k1, object) returns a key k2 (links to entry within T2)

To hash h2( object.class, object ), first hash gives a key to location of object in an entire arrangement of two hash tables.

Why Can't we create Hash map with key and value both of object type and overwrite the methods for specific type

Please find the Implementation

public class CustomHashMap {

    private LinkedHashEntry[] hashTable;
    private static final int HASH_LENGTH = 100;
    public CustomHashMap(){
        hashTable = new LinkedHashEntry[HASH_LENGTH];
    }

    public void put(Object key,Object value){
        LinkedHashEntry node = getNode(key);

        if(node == null){
            hashTable[getHashCode(key)]=new LinkedHashEntry(key, value);
            return;
        }

        while(node.hasNext() && !(node.getKey().equals(key)))
              node=node.next;

        //updation
        if(key.equals(node.getKey()))
            node.value=value;
        System.out.println(" Node "+node.getKey()+"  "+ node.value+ "  "+node.next);
        //addition
        LinkedHashEntry newEntry = new LinkedHashEntry(key, value);
                        node.next=newEntry;

        System.out.println(" Node "+node.getKey()+"  "+ node.value+ "  "+node.next);
        System.out.println(" newEntry "+newEntry.getKey()+"  "+ newEntry.value+ "  "+newEntry.next);
        System.out.println(newEntry);

    }

    public Object get(Object key){

        if(key == null)
            return null;

        LinkedHashEntry node = getNode(key);
          if(node == null)
             return null;

         while(node.hasNext() && !key.equals(node.getKey()))
               node=node.next;

        if(key.equals(node.getKey()))
            return node.value;

        return null;
    }

    public Boolean remove(Object key){

        if(key == null)
            return false;

        LinkedHashEntry node = getNode(key);
        LinkedHashEntry previousNode=node;

        while(node.hasNext() && !key.equals(node.getKey())){
              previousNode=node;
              node=node.next;
        }

              if(key.equals(node.getKey())){
                  previousNode.next=node.next;
                  node.next=null;
                  return true;
              }


        return false;
    }

    private LinkedHashEntry getNode(Object key) {
        System.out.println("getHashCode(key)   "+ getHashCode(key));
        return hashTable[getHashCode(key)];
    }

    private int getHashCode(Object key) {
        return (key.hashCode() %  HASH_LENGTH);
    }

    private class LinkedHashEntry{

        private Object key;
        private Object value;
        private LinkedHashEntry next;
        LinkedHashEntry(Object key,Object value){

             this.key=key;
             this.value=value;
             this.next=null;
        }

        Object getKey(){
            return key;
        }

        Boolean hasNext(){
            return (next != null);
        }


    }


    public static void main(String ... s){
        CustomHashMap customHashMap = new CustomHashMap();

        customHashMap.put("hi","hi");
        customHashMap.put(29,"hi bye");

    }
}

What the problem? Implement Map<?,?> interface

public class Hash <Key, Value>{

Key ob1;
Value ob2;

Hash(Key ob1, Value ob2)
{
this.ob1 = ob1;
this.ob2 = ob2;
}

Key getOb1()
{
return ob1;
}

Value getOb2()
{
return ob2;
}
}

public class Hash <Key, Value>{

	Key ob1;
	Value ob2;
	
	Hash(Key ob1, Value ob2)
	{
		this.ob1 = ob1;
		this.ob2 = ob2;
	}
	
	Key getOb1()
	{
		return ob1;
	}
	
	Value getOb2()
	{
		return ob2;
	}
}