Java URL Value Check isValidURL(String url)

Description

is Valid URL

License

Open Source License

Declaration

public static boolean isValidURL(String url) 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

import java.net.MalformedURLException;

public class Main {
    public static boolean isValidURL(String url) {
        if (url.length() < 10)
            return false;
        url = url.trim();//  w  w w  .  j  ava  2s .  com

        if (url.startsWith("http://") || url.startsWith("https://") || url.startsWith("ftp://")) {
            String host = null;
            try {
                host = getHostName(url);
            } catch (MalformedURLException e) {
                return false;
            }

            if (!isValidHostString(host))
                return false;
            if (host.contains(".."))
                return false;
        } else {//unknown schema
            return false;
        }

        //it seems right
        return true;
    }

    public static String getHostName(String url) throws MalformedURLException {
        if (url == null || url.length() == 0)
            return "";
        url = url.toLowerCase();
        if (!url.startsWith("http://") && !url.startsWith("https://") && !url.startsWith("ftp://"))
            throw new MalformedURLException("Unknown schema!");

        int doubleslash = url.indexOf("//");
        doubleslash += 2;

        int end = url.length();

        int idx = url.indexOf('/', doubleslash);
        if (idx > 0 && idx < end)
            end = idx;

        idx = url.indexOf(':', doubleslash);
        if (idx > 0 && idx < end)
            end = idx;

        idx = url.indexOf('&', doubleslash);
        if (idx > 0 && idx < end)
            end = idx;

        idx = url.indexOf('=', doubleslash);
        if (idx > 0 && idx < end)
            end = idx;

        idx = url.indexOf('#', doubleslash);
        if (idx > 0 && idx < end)
            end = idx;

        idx = url.indexOf('?', doubleslash);
        if (idx > 0 && idx < end)
            end = idx;

        return url.substring(doubleslash, end);
    }

    static public final boolean isValidHostString(String str) {
        str = str.trim();
        for (int i = 0; i < str.length(); i++)
            if (!isValidHostChar(str.charAt(i)))
                return false;
        if (str.startsWith("-") || str.endsWith("-"))
            return false;
        if (str.startsWith(".") || str.endsWith("."))
            return false;
        if (str.startsWith(":") || str.endsWith(":"))
            return false;

        int colon_count = 0;
        for (int i = 0; i < str.length(); i++)
            if (str.charAt(i) == ':')
                colon_count++;
        if (colon_count > 1)
            return false;

        if (str.endsWith("_"))
            return false;

        return true;
    }

    static private final boolean isValidHostChar(char ch) {
        return isAsciLetter(ch) || isAsciDigit(ch) || ch == '-' || ch == '.' || ch == '_' || ch == ':';
    }

    static private final boolean isAsciLetter(char ch) {
        return (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z');
    }

    static private final boolean isAsciDigit(char ch) {
        return (ch >= '0' && ch <= '9');
    }
}

Related

1. isValidURL(CharSequence urlStr)
2. isValidURL(final String candidateString)
3. isValidURL(String link)
4. isValidURL(String url)
5. isValidURL(String url)
6. isValidUrl(String url)
7. isValidURL(String URL_String)
8. isValidURL(String urlStr)
9. isValidURL(String urlStr)