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

问题

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)\\://

回答1:

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)://.*$"));

回答2:

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.

回答3:

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

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

回答4:

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

回答5:

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

来源：https://stackoverflow.com/questions/8061302/regex-to-check-with-starts-with-http-https-or-ftp

标签

java

regex

startswith