RandomUrlGenerator

RandomUrlGenerator.java

import org.apache.commons.lang3.RandomStringUtils;

import java.security.SecureRandom;
import java.util.Random;
import java.util.stream.IntStream;

import static java.util.stream.Collectors.joining;

public final class RandomUrlGenerator {

    private RandomUrlGenerator() {
        // not allowed to construct
    }

    private static final Random random = new SecureRandom();

    private static final String[] schemes = new String[]{
            "http", "https"
    };

    private static final String[] endings = new String[]{
            "io", "com", "de", "co.uk", "tv", "koeln", "price", "adult"
    };

    public static String url() {
        return host() + path() + queryParameter();
    }

    public static String queryParameter() {
        return queryParameter(random.nextInt(5));
    }

    private static String queryParameter(int size) {
        String queryParameter = IntStream.range(0, size)
                .mapToObj(
                        i -> RandomStringUtils.randomAlphabetic(4, 10).toLowerCase() + "=" + RandomStringUtils.randomAlphabetic(4, 10).toLowerCase()
                )
                .collect(joining("&", "?", ""));
        if (queryParameter.equals("?")) {
            return "";
        }
        return queryParameter;
    }

    public static String path() {
        return path(random.nextInt(5));
    }

    private static String path(int pathSegments) {
        return IntStream.range(1, pathSegments).mapToObj(i -> RandomStringUtils.randomAlphabetic(4, 10).toLowerCase()).collect(joining("/", "/", ""));
    }

    public static String host() {
        return choice(schemes) + "://www." + RandomStringUtils.randomAlphabetic(4, 10).toLowerCase() + "." + choice(endings);
    }

    public static <T> T choice(T[] array) {
        return array[random.nextInt(array.length)];
    }
}

RandomUrlGeneratorTest.java

import org.junit.Before;
import org.junit.Test;

import java.net.MalformedURLException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;

public class RandomUrlGeneratorTest {

    @Before
    public void setup() {
    }

    @Test
    public void urlIsValid() throws MalformedURLException, URISyntaxException {
        for (int i = 0; i < 100000; i++) {
            String randomUrl = RandomUrlGenerator.url();
            new URI(randomUrl);
            new URL(randomUrl);
        }
    }

}