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Apache Commons Compress defines an API for working with compression and archive formats. These include bzip2, gzip, pack200, LZMA, XZ, Snappy, traditional Unix Compress, DEFLATE, DEFLATE64, LZ4, Brotli, Zstandard and ar, cpio, jar, tar, zip, dump, 7z, arj.

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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.compress.utils;

import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.ServiceConfigurationError;
import java.util.ServiceLoader;

/**
 * Iterates all services for a given class through the standard
 * {@link ServiceLoader} mechanism.
 *
 * @param 
 *            The service to load
 * @since 1.13
 */
public class ServiceLoaderIterator implements Iterator {

    private E nextServiceLoader;
    private final Class service;
    private final Iterator serviceLoaderIterator;

    public ServiceLoaderIterator(final Class service) {
        this(service, ClassLoader.getSystemClassLoader());
    }

    public ServiceLoaderIterator(final Class service, final ClassLoader classLoader) {
        this.service = service;
        final ServiceLoader serviceLoader = ServiceLoader.load(service, classLoader);
        serviceLoaderIterator = serviceLoader.iterator();
        nextServiceLoader = null;
    }

    private boolean getNextServiceLoader() {
        while (nextServiceLoader == null) {
            try {
                if (!serviceLoaderIterator.hasNext()) {
                    return false;
                }
                nextServiceLoader = serviceLoaderIterator.next();
            } catch (final ServiceConfigurationError e) {
                if (e.getCause() instanceof SecurityException) {
                    // Ignore security exceptions
                    // TODO Log?
                    continue;
                }
                throw e;
            }
        }
        return true;
    }

    @Override
    public boolean hasNext() {
        return getNextServiceLoader();
    }

    @Override
    public E next() {
        if (!getNextServiceLoader()) {
            throw new NoSuchElementException("No more elements for service " + service.getName());
        }
        final E tempNext = nextServiceLoader;
        nextServiceLoader = null;
        return tempNext;
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException("service=" + service.getName());
    }

}