1. URL:

• It is a class that is used to represent URL

• It is a package of java.net.

• A url is devided into the many sections;

• Example program 💯

     URLMthod.java
  

output://

     Protocol:- https

     Domain/Host:- www.github.com

     Authority:- www.github.com:3000

     Port Number:- 3000

     Default Port Number:- 443

     Path:- /iamisha

     File:- /iamisha?tab=repositories

     Query String :- tab=repositories

      Anchor/Reference:- git

      URI:-https://www.github.com:3000/iamisha?tab=repositories#git

      URL String:- https://www.github.com:3000/iamisha?tab=repositories#git

2. URLConnection:

• URLConnection class is used to read/write data string of a given URL.

• The java URLConnection class represents the communication between the URL and the application.

• The openConnection() method of the URL class returns the object of the URLConnection class.

• SYNTAX:-

    public URLConnection openConnection throws IOException{
  

• Example program

    URLConnectionExam.java
  

3. ResponseHeader

• It helps to print the Httpresponse

• Example:

   PrintHttpResponse.java
  

• Output://

    Response code:- 200
  
    Response Message:- OK
  
    Connection Timeout:- 0
  
    Encoding:- null
  
    Length of content:- -1
  
    Content type:- text/html; charset=utf-8
  
    Request Type:- GET
  
    Date:- 1673782416000
  

4. HashMap

• It is an interface that contain values based on keys.

• Not ordered

• 'Key' should be unique.

• 'Value' can be repeated.

• It implements interface Map.

• It is found in java.util package.

• Example:-

    HashMapExam.java
  

output://

    using put() method to insert the key and value

    {Isha=201710, Priyanka=201725}

    Printing if the specified hashmap contains the following key or not

    true

    false

    true

    false

    key is present in the map

    201710

    get method simply prints the value of the specified key if the key is present otherwise it returns null

    201710

    null

    only for test purpose

    1 2 33 

    1 2 33 

    Printing the key with their values through entrySet()

    Isha

    201710

    Priyanka

    201725

    Printing the key with their values through keySet()

    Isha 201710

    Priyanka 201725

    removing any pair in HashMap

    {Priyanka=201725}

Qn:- Write a java program to print all HTTP Request Headers

Solution:-

    Header.java

5. InetAddress

• It is a class that represents IP addresses.

• InetAddress class provides methods to get the IP addresses of any host name.

• Some of the method are:-

    1. public String getHostName():-
    Returns the hostname of the Address.
  
    2. public String getHostAddress():-
    Returns the IP Address in string format.
  
    3. public static InetAddress getLocalHost() throws UnknownHostException:-
    Returns the instances of the InetAdddress containing local host name and address.
  
    4.public static InetAddress getByName() throws UnknownHostException:-
    Returns the instances of the InetAddress containing LocalHost IP and name.
  
    5. public static  InetAddress getAllByName() throws UnknownHostException:- 
    Returns the  array of list of the InetAddress.
  

• InetAddress is a class that allows us to work with IPAddress belongs to java.net package.

• It is a base class of both Inet4Address(Ipv4) and Inet6Address(Ipv6)

• Example:-

    InetAddressExam.java
  

• Output://

    Host Name:- www.ishahitang.com.np
  
    IP Address:- 104.21.55.131
    
   Local Host Name:- isha-81wd
   
   LocalHost IP:- 127.0.1.1
  

Qn. Display all the IP addresses associated with the given URL.

• Solution:

    DisplayIPAddress.java