URL class in Java with Examples

• The URL class is the gateway to any of the resource available on the internet. A Class URL represents a Uniform Resource Locator, which is a pointer to a “resource” on the World Wide Web. A resource can point to a simple file or directory, or it can refer to a more complicated object, such as a query to a database or to a search engine

What is a URL?

• As many of you must be knowing that Uniform Resource Locator-URL is a string of text that identifies all the resources on Internet, telling us the address of the resource, how to communicate with it and retrieve something from it.

A Simple URL looks like:
URL Class

Components of a URL:-
A URL can have many forms. The most general however follows three-components system-

• Protocol: HTTP is the protocol here
• Hostname: Name of the machine on which the resource lives.
• File Name: The path name to the file on the machine.
• Port Number: Port number to which to connect (typically optional).

Some constructors for URL class:-

• URL(String address) throws MalformedURLException: It creates a URL object from the specified String.
• URL(String protocol, String host, String file): Creates a URL object from the specified protcol, host, and file name.
• URL(String protocol, String host, int port, String file): Creates a URL object from protocol, host, port and file name.
• URL(URL context, String spec): Creates a URL object by parsing the given spec in the given context.
• URL(String protocol, String host, int port, String file, URLStreamHandler handler):-
• Creates a URL object from the specified protocol, host, port number, file, and handler.
• URL(URL context, String spec, URLStreamHandler handler):-
• Creates a URL by parsing the given spec with the specified handler within a specified context.

Sample Program:

// Java program to demonstrate working of URL
import java.net.MalformedURLException;
import java.net.URL;

public class URLclass1
{
public static void main(String[] args)
throws MalformedURLException
{

// creates a URL with string representation.
URL url1 =
new URL("https://www.google.co.in/?gfe_rd=cr&ei=ptYq" +
"WK26I4fT8gfth6CACg#q=prutor+dot+ai+java");

// creates a URL with a protocol,hostname,and path
URL url2 = new URL("http", "www.prutor.ai",
"/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=prutor+dot+ai+java");

// 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 defalut port
System.out.println("Default port:- " +
url3.getDefaultPort());

// retrieve the query part of URL
System.out.println("Query:- " + url3.getQuery());

// retrive the path of URL
System.out.println("Path:- " + url3.getPath());

// retrive the file name
System.out.println("File:- " + url3.getFile());

// retrieve the reference
System.out.println("Reference:- " + url3.getRef());
}
}
Result :

https://www.google.co.in/?gfe_rd=cr&ei=ptYqWK26I4fT8gfth6CACg#q=prutor+dot+ai+java
https://www.prutor.ai/jvm-works-jvm-architecture/

Different components of the URL3-
Protocol:- https
Hostname:- www.google.co.in
Default port:- 443
Query:- q=gnu&rlz=1C1CHZL_enIN714IN715&oq=gnu&aqs=chrome..69i57j69i60l5.653j0j7&sourceid=chrome&ie=UTF-8
Path:- /search
File:- /search?q=gnu&rlz=1C1CHZL_enIN714IN715&oq=gnu&aqs=chrome..69i57j69i60l5.653j0j7&sourceid=chrome&ie=UTF-8
Reference:- q=prutor+dot+ai+java

Explanation of some methods used in the above program is as follows:-

• public String toString(): As in any class, toString() returns the string representation of the given URL object.
• public String getAuthority(): returns the authority part of URL or null if empty.
• public String getPath(): returns the path of the URL, or null if empty.
• public String getQuery(): returns the query part of URL. Query is the part after the ‘?’ in the URL. Whenever logic
• is used to display the result, there would be a query field in URL. It is similar to querying a database.
• public String getHost(): return the hostname of the URL in IPv6 format.
• public String getFile(): returns the file name.
• public String getRef(): Returns the reference of the URL object. Usually, the reference is the part marked by a ‘#’ in the URL. You can see the working example by querying anything on google and seeing the part after ‘#’.
• public int getPort(): returns the port associated with the protocol specified by the URL.
• public int getDefaultPort: returns the default port used.
• public String getProtocol(): returns the protocol used by the URL.