URL Class in Java

Anybody who uses the internet these days would have come across a URL. It is a unique string of text that is an identity for the resources available on the internet. To put it in simple words, a URL is an address for the resources that we can find on the internet. This article explains the URL class in Java. Let’s start!!

What is URL?

The term URL is an acronym for Uniform Resource Locator. It denotes a resource that is present on the World Wide Web. This resource might be an HTML page, file, or document that is present on the World Wide Web.

Segments of a URL:

Though a URL might consist of several components, it consists of three main parts.:

1. Protocol: In the above-given example, HTTP is the protocol. Some other examples of protocols are HTTPS, FTP, and File.

2. Server name or IP address: The server machine where the resources are present is denoted as the server’s name. Here, firstcode.com is the server name.

3. Filename: Here, the file name is “java-class-and-objects”.

4. Port number: Port number helps the URL connect with the web. In case of not explicitly mentioning the URL, the default port number is used.

Java URL Class

The Java URL is the gateway to access any resource that is present on the web. The object of the java.net.URL class denotes the URL and manages all the details available in the URL string. This class consists of various methods to create an object of the URL class.

Methods of Java URL Class:

Creating URL with Component Parts:

Let us now see how to create a URL using the SUL components like hostname, filename, and protocol.

Sample code to create a URL with the URL components:

import java.net.MalformedURLException;
import java.net.URL;
public class URLClassDemo
{
public static void main(String[ ] args) throws MalformedURLException
{
String protocol = "http";
String host = "firstcode.com";
String file = "/courses/java-url-class/";
URL url = new URL(protocol, host, file);   
System.out.println("The URL is: " +url.toString());
}
}

Output:

Sample program to implement the URL Class of Java:

import java.net.MalformedURLException;
import java.net.URL;
public class URLClassDemo
{
public static void main(String[] args) throws MalformedURLException
{
URL url1 = new URL("https://firstcode.com/courses/java-encapsulation/");
System.out.println("url1 is: " +url1.toString());
System.out.println("\nVarious components of the url1");
System.out.println("Protocol: " + url1.getProtocol());
System.out.println("Hostname: " + url1.getHost());
System.out.println("Port: " + url1.getPort());
System.out.println("Default port: " + url1.getDefaultPort());
System.out.println("Query: " + url1.getQuery());
System.out.println("Path: " + url1.getPath());
System.out.println("File: " + url1.getFile());
System.out.println("Reference: " + url1.getRef());
System.out.println("Authority: " + url1.getAuthority());
}

Output:

URL Connection class in Java:

The URLConnection class in Java is important to represent a connection or communication between an application and the URL. it helps the programmers to read and write data to the given resource of the URL.

The java.net.URLConnection is an abstract class that has its subclasses representing the different types of URL connections.

For example:

• The openConnection() method returns the object of the HttpURLConnection class. This takes place when we connect to a URL using the HTTP protocol.
• The openConnection() method returns the object of a JarURLConnection class. this happens if we connect a JAR file to a URL.

Java OpenConnection() method:

We can attain the object of the URLConnection class with the openConnection() method of the URL class.

Syntax:

public URLConnection openConnection() throws IOException{}

Methods of URL Connection Class in Java:

Example of the URLConnection class:

As we just saw the various methods that are present in the URLConnectionDemo class, let us see an example program to implement it.

Sample program to implement URLConnection class:

import java.net.*;
import java.io.*;
public class URLConnectionDemo
{
public static void main(String[] args) throws MalformedURLException
{
try{
URL url = new URL("https://www.firstcode.com");
URLConnection urlConnection = url.openConnection();
HttpURLConnection connection = null;
if(urlConnection instanceof HttpURLConnection)
{
connection = (HttpURLConnection) urlConnection; 
}
else
{
System.out.println("Please enter a HTTP URL: ");
return;
}
BufferedReader in = new BufferedReader(
new InputStreamReader(connection.getInputStream()));
String urlString = " ";
String current;
while((current = in.readLine()) != null)
{
urlString += current;
}
System.out.println(urlString);
} catch (IOException e)
{
e.printStackTrace();
}
}
}

Output:

Illustration methods of Java URL class:

import java.net.*;
public class FirstCode
{
public static void main(String[] args)throws Exception{
String url="https://first-code/blogs/java-tutorial/";
URL testurl= new URL(url);
System.out.println("The String representation of the URL -> "+testurl.toString());
System.out.println("The Authority of the URL -> "+testurl.getAuthority());
System.out.println("The Path of the URL -> "+testurl.getPath());
System.out.println("The Query of the URL -> "+testurl.getQuery());
System.out.println("The Host of the URL -> "+testurl.getHost());
System.out.println("The File of the URL -> "+testurl.getFile());
System.out.println("The Port of the URL -> "+testurl.getPort());
System.out.println("The Default port of the URL -> "+testurl.getDefaultPort());
System.out.println("The Protocol of the URL -> "+testurl.getProtocol());
System.out.println("As no certain values can be parsed, the results are null or -1 in various cases, but there are no particular values.");
 
}
}

Output:

As no certain values can be parsed, the results are null or -1 in various cases, but there are no particular values.

Sample program to implement url class in Java:

import java.net.MalformedURLException;
import java.net.URL;
public class FirstCode
{
public static void main(String[] args)throws MalformedURLException
{
URL url1 = new URL("https://www.google.co.in/?gfe_rd=cr&ei=ptYq" + "WK26I4fT8gfth6CACg#q=first+code+java+tutorials");
 
// creates a URL with a protocol,hostname,and path
URL url2 = new URL("http", "www.firstcode.com", "/jvm-works-jvm-architecture/");
 
URL url3 = new URL("https://www.google.co.in/search?"+ "q=gnu&rlz=1C1CHZL_enIN71" + "4IN715&oq=gnu&aqs=chrome..69i57j6" +"9i60l5.653j0j7&sourceid=chrome&ie=UTF" + "-8#q=first+code+java+tutorials");
 
// print the string representation of the URL.
System.out.println(url1.toString());
System.out.println(url2.toString());
System.out.println();
System.out.println("Different components of the URL3-");
 
// retrieve the protocol for the URL
System.out.println("Protocol:- " + url3.getProtocol());
 
// retrieve the hostname of the url
System.out.println("Hostname:- " + url3.getHost());
 
// retrieve the default port
System.out.println("Default port:- " +url3.getDefaultPort());
 
// retrieve the query part of URL
System.out.println("Query:- " + url3.getQuery());
 
// retrieve the path of URL
System.out.println("Path:- " + url3.getPath());
 
// retrieve the file name
System.out.println("File:- " + url3.getFile());
 
// retrieve the reference
System.out.println("Reference:- " + url3.getRef());
}
}

Output:

Conclusion

The URL class is inevitable in the internet era. In this tutorial, we learned about the Java URL, its constructors, and methods. Now, you can easily establish the URL connection class to connect with an application.