@@ -0,0 +1,2124 @@
+/*%0A * Licensed to the Apache Software Foundation (ASF) under one or more%0A * contributor license agreements.  See the NOTICE file distributed with%0A * this work for additional information regarding copyright ownership.%0A * The ASF licenses this file to You under the Apache License, Version 2.0%0A * (the %22License%22); you may not use this file except in compliance with%0A * the License.  You may obtain a copy of the License at%0A *%0A *      http://www.apache.org/licenses/LICENSE-2.0%0A *%0A * Unless required by applicable law or agreed to in writing, software%0A * distributed under the License is distributed on an %22AS IS%22 BASIS,%0A * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.%0A * See the License for the specific language governing permissions and%0A * limitations under the License.%0A */%0Apackage org.apache.pdfbox.pdfwriter;%0A%0Aimport java.io.BufferedOutputStream;%0Aimport java.io.ByteArrayOutputStream;%0Aimport java.io.IOException;%0Aimport org.apache.pdfbox.pdmodel.PDDocument;%0Aimport org.apache.pdfbox.pdmodel.PDPage;%0Aimport org.junit.Test;%0A%0Apublic class COSWriterTest%0A%7B%0A    /**%0A     * PDFBOX-4241: check whether the output stream is closed twice.%0A     * %0A     * @throws IOException %0A     */%0A    @Test%0A    public void testPDFBox4241() throws IOException%0A    %7B%0A        try (PDDocument doc = new PDDocument())%0A        %7B%0A            %0A            PDPage page = new PDPage();%0A            doc.addPage(page);%0A            doc.save(new BufferedOutputStream(new ByteArrayOutputStream(1024)%0A            %7B%0A                private boolean open = true;%0A%0A                @Override%0A                public void close() throws IOException%0A                %7B%0A                    //Thread.dumpStack();%0A%0A                    open = false;%0A                    super.close();%0A                %7D%0A%0A                @Override%0A                public void flush() throws IOException%0A                %7B%0A                    if (!open)%0A                    %7B%0A                        throw new IOException(%22Stream already closed%22);%0A                    %7D%0A%0A                    //Thread.dumpStack();%0A                %7D%0A            %7D));%0A        %7D%0A    %7D%0A%7D%0A

add test that stream is closed only once, as suggested by Harald Kuhr