Regex to check with starts with http://, https:// or ftp://

Question

I am framing a regex to check if a word starts with http:// or https:// or ftp://, my code is as follows,

     public static void main(String[] args) {
    try{
        String test = "http://yahoo.com";
        System.out.println(test.matches("^(http|https|ftp)://"));
    } finally{

    }
}

It prints false. I also checked stackoverflow post Regex to test if string begins with http:// or https://

The regex seems to be right but why is it not matching?. I even tried ^(http|https|ftp)\:// and ^(http|https|ftp)\\://

Why a regex? Why not try to construct a URL or URI and get the protocol from that? — user207421, Nov 09 '11 at 06:47

score 107 · Accepted Answer · edited May 23 '17 at 12:26

107

You need a whole input match here.

System.out.println(test.matches("^(http|https|ftp)://.*$"));

Edit:(Based on @davidchambers's comment)

System.out.println(test.matches("^(https?|ftp)://.*$"));

edited May 23 '17 at 12:26

Community

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answered Nov 09 '11 at 06:48

Prince John Wesley

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You could also use `(https?|ftp)` if preferred. – davidchambers Nov 09 '11 at 07:03
@davidchambers: +1. the goal is to convey that the `matches` method will match the whole input. i'll update your input – Prince John Wesley Nov 09 '11 at 07:06
You finished with .*$ Can you please elaborate what does it mean (I understand that it gets the entire line but in plain English, how would you explain .*$ thanks! – adhg Mar 22 '17 at 16:10
2

@adhg `$` indicates end of line. `.*` matches any character zero or more times. – Prince John Wesley Mar 23 '17 at 18:36

score 35 · Answer 2 · answered Nov 09 '11 at 06:54

35

Unless there is some compelling reason to use a regex, I would just use String.startsWith:

bool matches = test.startsWith("http://")
            || test.startsWith("https://") 
            || test.startsWith("ftp://");

I wouldn't be surprised if this is faster, too.

answered Nov 09 '11 at 06:54

Randall Cook

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I'd be surprised if this wasn't slower (compared to a compiled regex that is), but have to test to find out. – Joel Nov 17 '15 at 19:00

score 5 · Answer 3 · answered Sep 09 '14 at 03:31

5

If you wanna do it in case-insensitive way, this is better:

System.out.println(test.matches("^(?i)(https?|ftp)://.*$"));

answered Sep 09 '14 at 03:31

user1079877

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score 4 · Answer 4 · answered May 11 '18 at 12:07

I think the regex / string parsing solutions are great, but for this particular context, it seems like it would make sense just to use java's url parser:

https://docs.oracle.com/javase/tutorial/networking/urls/urlInfo.html

Taken from that page:

import java.net.*;
import java.io.*;

public class ParseURL {
    public static void main(String[] args) throws Exception {

        URL aURL = new URL("http://example.com:80/docs/books/tutorial"
                           + "/index.html?name=networking#DOWNLOADING");

        System.out.println("protocol = " + aURL.getProtocol());
        System.out.println("authority = " + aURL.getAuthority());
        System.out.println("host = " + aURL.getHost());
        System.out.println("port = " + aURL.getPort());
        System.out.println("path = " + aURL.getPath());
        System.out.println("query = " + aURL.getQuery());
        System.out.println("filename = " + aURL.getFile());
        System.out.println("ref = " + aURL.getRef());
    }
}

yields the following:

protocol = http
authority = example.com:80
host = example.com
port = 80
path = /docs/books/tutorial/index.html
query = name=networking
filename = /docs/books/tutorial/index.html?name=networking
ref = DOWNLOADING

score 1 · Answer 5 · answered Nov 09 '11 at 06:53

1

test.matches() method checks all text.use test.find()

answered Nov 09 '11 at 06:53

shift66

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Victor Choy · Answer 6 · 2023-01-06T08:35:55.830

Add a verification between startsWith and matches.

import java.net.URL


fun main(args: Array<String>) {
    
    val IMAGE_SERVER = "https://google.com/file/"
    val IMAGE_REG: String by lazy {
        val url = URL(IMAGE_SERVER)
        "^(http|https)://${url.host}${url.path}.*\$"
    }
    
    val regx = Regex(IMAGE_REG)
    println(IMAGE_REG)
    

    var begin = System.nanoTime()
    var aa = IMAGE_SERVER.startsWith(IMAGE_SERVER)
    println("startsWith:"+ (System.nanoTime()-begin))
    println("startsWith:"+ aa)
    
    begin = System.nanoTime()
    aa = IMAGE_SERVER.matches(regx)
    println("matches:"+ (System.nanoTime()-begin))
    println("matches:"+ aa)
    

}

startsWith:3755625
startsWith:true
matches:174250
matches:true

matches is 174us, startswith is 3.755ms

matches is much better than startsWith on performance and code cleanness in the scenario.

Regex to check with starts with http://, https:// or ftp://

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