Hashtable

Hastable h = new Hashtable()
- Empty hash table with initial capacity 11
- Load Factor 0.75
Hastable h = new Hashtable(int initialCapacity)
- Load Factor 0.75
- InitialCapacity set via constructor
Hastable h = new Hashtable(int initialCapacity, float fillRatio)
- LoadFactor and Initital Capacity both is given as input
Hastable h = new Hashtable(Map m)
- Cross collection conversion

Internal Working of a Hashtable

Hashtable works on Hashing principles
Object class has a hashCode() method which returns a integer value which is the HashCode

Example :

For our example we will store objects of class Temp in the Hastable

Explaination :

Temp Class

We have overridden the hashCode() of the Temp class so that an integer that we pass is the HashCode of for that object
We have overridden the toString() method so that the integer itself is returned

Main Method Execution

We create a Hashtable with name h, since no initial capacity is passed the default value is 11
- A bucket is created with size 11
We add 1st value to it i.e new Temp(5),”A”
- Now is here the key is object Temp(5) and the value is A
- We have overridden the Hashcode of the temp class and we know of a fact that its hashcode is 5
- Now we calculate the location of value “A” in the bucker
- We calculate that by formula hash%capacity i.e 5%11 = 5
- So the value 5=A will be stored at location 5 in the bucket
Similarly for new Temp(2),”B” location 2
Similarly for new Temp(6),”C” location 6
Similarly for new Temp(15),”D” location 4
Similarly for new Temp(23),”E” location 1
For new Temp(16),”F” we have hashcollision
- For hashcollision we use the same bucket a location right to it
Thus all the values are stored in the HashTable
Printing of Hashtable
- Printing of Hashtable happens from top to bottom ie. from index 10 to 0
- If 2 values are present inside a bucket then from right to left
- Hence the output 6=C, 16=F, 5=A, 15=D, 2=B, 23=E}