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Apache Commons Lang, a package of Java utility classes for the classes that are in java.lang's hierarchy, or are considered to be so standard as to justify existence in java.lang. The code is tested using the latest revision of the JDK for supported LTS releases: 8, 11, 17 and 21 currently. See https://github.com/apache/commons-lang/blob/master/.github/workflows/maven.yml Please ensure your build environment is up-to-date and kindly report any build issues.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.lang3;

import java.net.URL;
import java.net.URLClassLoader;
import java.util.Arrays;
import java.util.Objects;

/**
 * Helps work with {@link ClassLoader}.
 *
 * @since 3.10
 */
public class ClassLoaderUtils {

    private static final URL[] EMPTY_URL_ARRAY = new URL[] {};

    /**
     * Gets the system class loader's URLs, if any.
     *
     * @return the system class loader's URLs, if any.
     * @since 3.13.0
     */
    public static URL[] getSystemURLs() {
        return getURLs(ClassLoader.getSystemClassLoader());
    }

    /**
     * Gets the current thread's context class loader's URLs, if any.
     *
     * @return the current thread's context class loader's URLs, if any.
     * @since 3.13.0
     */
    public static URL[] getThreadURLs() {
        return getURLs(Thread.currentThread().getContextClassLoader());
    }

    private static URL[] getURLs(final ClassLoader cl) {
        return cl instanceof URLClassLoader ? ((URLClassLoader) cl).getURLs() : EMPTY_URL_ARRAY;
    }

    /**
     * Converts the given class loader to a String calling {@link #toString(URLClassLoader)}.
     *
     * @param classLoader to URLClassLoader to convert.
     * @return the formatted string.
     */
    public static String toString(final ClassLoader classLoader) {
        if (classLoader instanceof URLClassLoader) {
            return toString((URLClassLoader) classLoader);
        }
        return Objects.toString(classLoader);
    }

    /**
     * Converts the given URLClassLoader to a String in the format {@code "URLClassLoader.toString() + [URL1, URL2, ...]"}.
     *
     * @param classLoader to URLClassLoader to convert.
     * @return the formatted string.
     */
    public static String toString(final URLClassLoader classLoader) {
        return classLoader != null ? classLoader + Arrays.toString(classLoader.getURLs()) : "null";
    }
}