A HashTable in Java is a type of map that stores key-value pairs. It keeps keys unique, and does not allow null values.

Example: Adding and Retrieving Values from HashTable

package com.quipoin;

import java.util.Hashtable;
import java.util.Iterator;
import java.util.Set;

public class HashtableDemo {
	public static void main(String[] args) {
		Hashtable<Integer, String> ht=new Hashtable<>();

		ht.put(100, "Raj");
		ht.put(102, "Keshav");
		ht.put(101, "Bharath");
		ht.put(103, "Prasad");

		System.out.println("Id\tName");
		System.out.println("---------------");
		Set<Integer> id=ht.keySet();
		Iterator<Integer> it=id.iterator();

		while(it.hasNext()) {
			Integer key=it.next();
			String value=ht.get(key);
			System.out.println(key+"\t"+value);
		}
	}
}

Output:

Id	Name
---------------
103	Prasad
102	Keshav
101	Bharath
100	Raj

Example: Removing an Entry form HashTable

package com.hashtable;

import java.util.Hashtable;
import java.util.Iterator;
import java.util.Set;

public class HashtableDemo2 {
	public static void main(String[] args) {
		Hashtable<Integer, String> ht=new Hashtable<>();

		ht.put(100, "Amith");
		ht.put(102, "Ravi");
		ht.put(101, "Vijay");
		ht.put(103, "Rahul");

		System.out.println("Before remove:\n"+ht);

		ht.remove(102);
		System.out.println("After remove:\n"+ht);
	}
}

Output:

Before remove:
{103=Rahul, 102=Ravi, 101=Vijay, 100=Amith}
After remove:
{103=Rahul, 101=Vijay, 100=Amith}