jdk/test/java/io/FileDescriptor/Sharing.java - platform/libcore - Git at Google

 /*
  * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */

 /*
  * @test
  * @bug 7105952 6322678 7082769
  * @summary Improve finalisation for FileInputStream/FileOutputStream/RandomAccessFile
  * @run main/othervm Sharing
  */

 import java.io.*;
 import java.nio.channels.FileChannel;
 import java.nio.channels.FileLock;
 import java.util.concurrent.CountDownLatch;

 public class Sharing {

     final static int numFiles = 10;
     volatile static boolean fail;

     public static void main(String[] args) throws Exception {
         TestFinalizer();
         TestMultipleFD();
         TestIsValid();
         MultiThreadedFD();
         TestCloseAll();
     }

     /**
      * Finalizer shouldn't discard a file descriptor until all streams have
      * finished with it.
      */
     private static void TestFinalizer() throws Exception {
         FileDescriptor fd = null;
         File tempFile = new File("TestFinalizer1.txt");
         tempFile.deleteOnExit();
         try (Writer writer = new FileWriter(tempFile)) {
             for (int i=0; i<5; i++) {
                 writer.write("test file content test file content");
             }
         }

         FileInputStream fis1 = new FileInputStream(tempFile);
         fd = fis1.getFD();
         // Create a new FIS based on the existing FD (so the two FIS's share the same native fd)
         try (FileInputStream fis2 = new FileInputStream(fd)) {
             // allow fis1 to be gc'ed
             fis1 = null;
             int ret = 0;
             while(ret >= 0) {
                 // encourage gc
                 System.gc();
                 // read from fis2 - when fis1 is gc'ed and finalizer is run, read will fail
                 System.out.print(".");
                 ret = fis2.read();
             }
         }

         // variation of above. Use RandomAccessFile to obtain a filedescriptor
         File testFinalizerFile = new File("TestFinalizer");
         RandomAccessFile raf = new RandomAccessFile(testFinalizerFile, "rw");
         raf.writeBytes("test file content test file content");
         raf.seek(0L);
         fd = raf.getFD();
         try (FileInputStream fis3 = new FileInputStream(fd)) {
             // allow raf to be gc'ed
             raf = null;
             int ret = 0;
             while (ret >= 0) {
                 // encourage gc
                 System.gc();
                 /*
                  * read from fis3 - when raf is gc'ed and finalizer is run,
                  * fd should still be valid.
                  */
                 System.out.print(".");
                 ret = fis3.read();
             }
         } finally {
             testFinalizerFile.delete();
         }
     }

     /**
      * Exercise FileDispatcher close()/preClose()
      */
     private static void TestMultipleFD() throws Exception {
         RandomAccessFile raf = null;
         FileOutputStream fos = null;
         FileInputStream fis = null;
         FileChannel fc = null;
         FileLock fileLock = null;

         File test1 = new File("test1");
         try {
             raf = new RandomAccessFile(test1, "rw");
             fos = new FileOutputStream(raf.getFD());
             fis = new FileInputStream(raf.getFD());
             fc = raf.getChannel();
             fileLock = fc.lock();
             raf.setLength(0L);
             fos.flush();
             fos.write("TEST".getBytes());
         } finally {
             if (fileLock != null) fileLock.release();
             if (fis != null) fis.close();
             if (fos != null) fos.close();
             if (raf != null) raf.close();
             test1.delete();
         }

         /*
          * Close out in different order to ensure FD is not
          * closed out too early
          */
         File test2 = new File("test2");
         try {
             raf = new RandomAccessFile(test2, "rw");
             fos = new FileOutputStream(raf.getFD());
             fis = new FileInputStream(raf.getFD());
             fc = raf.getChannel();
             fileLock = fc.lock();
             raf.setLength(0L);
             fos.flush();
             fos.write("TEST".getBytes());
         } finally {
             if (fileLock != null) fileLock.release();
             if (raf != null) raf.close();
             if (fos != null) fos.close();
             if (fis != null) fis.close();
             test2.delete();
         }

         // one more time, fos first this time
         File test3 = new File("test3");
         try {
             raf = new RandomAccessFile(test3, "rw");
             fos = new FileOutputStream(raf.getFD());
             fis = new FileInputStream(raf.getFD());
             fc = raf.getChannel();
             fileLock = fc.lock();
             raf.setLength(0L);
             fos.flush();
             fos.write("TEST".getBytes());
         } finally {
             if (fileLock != null) fileLock.release();
             if (fos != null) fos.close();
             if (raf != null) raf.close();
             if (fis != null) fis.close();
             test3.delete();
         }
     }

     /**
      * Similar to TestMultipleFD() but this time we
      * just get and use FileDescriptor.valid() for testing.
      */
     private static void TestIsValid() throws Exception {
         FileDescriptor fd = null;
         RandomAccessFile raf = null;
         FileOutputStream fos = null;
         FileInputStream fis = null;
         FileChannel fc = null;

         File test1 = new File("test1");
         try {
             raf = new RandomAccessFile(test1, "rw");
             fd = raf.getFD();
             fos = new FileOutputStream(fd);
             fis = new FileInputStream(fd);
         } finally {
             try {
                 if (fis != null) fis.close();
                 if (fd.valid()) {
                     throw new RuntimeException("[FIS close()] FileDescriptor shouldn't be valid");
                 }
                 if (fos != null) fos.close();
                 if (raf != null) raf.close();
             } finally {
                 test1.delete();
             }
         }

         /*
          * Close out in different order to ensure FD is
          * closed correctly.
          */
         File test2 = new File("test2");
         try {
             raf = new RandomAccessFile(test2, "rw");
             fd = raf.getFD();
             fos = new FileOutputStream(fd);
             fis = new FileInputStream(fd);
         } finally {
             try {
                 if (raf != null) raf.close();
                 if (fd.valid()) {
                     throw new RuntimeException("[RAF close()] FileDescriptor shouldn't be valid");
                 }
                 if (fos != null) fos.close();
                 if (fis != null) fis.close();
             } finally {
                 test2.delete();
             }
         }

         // one more time, fos first this time
         File test3 = new File("test3");
         try {
             raf = new RandomAccessFile(test3, "rw");
             fd = raf.getFD();
             fos = new FileOutputStream(fd);
             fis = new FileInputStream(fd);
         } finally {
             try {
                 if (fos != null) fos.close();
                 if (fd.valid()) {
                     throw new RuntimeException("[FOS close()] FileDescriptor shouldn't be valid");
                 }
                 if (raf != null) raf.close();
                 if (fis != null) fis.close();
             } finally {
                 test3.delete();
             }
         }
     }

     /**
      * Test concurrent access to the same FileDescriptor
      */
     private static void MultiThreadedFD() throws Exception {
         RandomAccessFile raf = null;
         FileDescriptor fd = null;
         int numThreads = 2;
         CountDownLatch done = new CountDownLatch(numThreads);
         OpenClose[] fileOpenClose = new OpenClose[numThreads];
         File MultipleThreadedFD = new File("MultipleThreadedFD");
         try {
             raf = new RandomAccessFile(MultipleThreadedFD, "rw");
             fd = raf.getFD();
             for(int count=0;count<numThreads;count++) {
                 fileOpenClose[count] = new OpenClose(fd, done);
                 fileOpenClose[count].start();
             }
             done.await();
         } finally {
             try {
                 if(raf != null) raf.close();
                 // fd should now no longer be valid
                 if(fd.valid()) {
                     throw new RuntimeException("FileDescriptor should not be valid");
                 }
                 // OpenClose thread tests failed
                 if(fail) {
                     throw new RuntimeException("OpenClose thread tests failed.");
                 }
             } finally {
                 MultipleThreadedFD.delete();
             }
         }
     }

     /**
      * Test closeAll handling in FileDescriptor
      */
     private static void TestCloseAll() throws Exception {
         File testFile = new File("test");
         testFile.deleteOnExit();
         RandomAccessFile raf = new RandomAccessFile(testFile, "rw");
         FileInputStream fis = new FileInputStream(raf.getFD());
         fis.close();
         if (raf.getFD().valid()) {
              throw new RuntimeException("FD should not be valid.");
         }

         // Test the suppressed exception handling - FileInputStream

         raf = new RandomAccessFile(testFile, "rw");
         fis = new FileInputStream(raf.getFD());
         BadFileInputStream bfis1 = new BadFileInputStream(raf.getFD());
         BadFileInputStream bfis2 = new BadFileInputStream(raf.getFD());
         BadFileInputStream bfis3 = new BadFileInputStream(raf.getFD());
         // extra test - set bfis3 to null
         bfis3 = null;
         try {
             fis.close();
         } catch (IOException ioe) {
             ioe.printStackTrace();
             if (ioe.getSuppressed().length != 2) {
                 throw new RuntimeException("[FIS]Incorrect number of suppressed " +
                           "exceptions received : " + ioe.getSuppressed().length);
             }
         }
         if (raf.getFD().valid()) {
             // we should still have closed the FD
             // even with the exception.
             throw new RuntimeException("[FIS]TestCloseAll : FD still valid.");
         }

         // Now test with FileOutputStream

         raf = new RandomAccessFile(testFile, "rw");
         FileOutputStream fos = new FileOutputStream(raf.getFD());
         BadFileOutputStream bfos1 = new BadFileOutputStream(raf.getFD());
         BadFileOutputStream bfos2 = new BadFileOutputStream(raf.getFD());
         BadFileOutputStream bfos3 = new BadFileOutputStream(raf.getFD());
         // extra test - set bfos3 to null
         bfos3 = null;
         try {
             fos.close();
         } catch (IOException ioe) {
             ioe.printStackTrace();
             if (ioe.getSuppressed().length != 2) {
                 throw new RuntimeException("[FOS]Incorrect number of suppressed " +
                           "exceptions received : " + ioe.getSuppressed().length);
             }
         }
         if (raf.getFD().valid()) {
             // we should still have closed the FD
             // even with the exception.
             throw new RuntimeException("[FOS]TestCloseAll : FD still valid.");
         }
     }

     /**
      * A thread which will open and close a number of FileInputStreams and
      * FileOutputStreams referencing the same native file descriptor.
      */
     private static class OpenClose extends Thread {
         private FileDescriptor fd = null;
         private CountDownLatch done;
         FileInputStream[] fisArray = new FileInputStream[numFiles];
         FileOutputStream[] fosArray = new FileOutputStream[numFiles];

         OpenClose(FileDescriptor filedescriptor, CountDownLatch done) {
             this.fd = filedescriptor;
             this.done = done;
         }

         public void run() {
              try {
                  for(int i=0;i<numFiles;i++) {
                      fisArray[i] = new FileInputStream(fd);
                      fosArray[i] = new FileOutputStream(fd);
                  }

                  // Now close out
                  for(int i=0;i<numFiles;i++) {
                      if(fisArray[i] != null) fisArray[i].close();
                      if(fosArray[i] != null) fosArray[i].close();
                  }

              } catch(IOException ioe) {
                  System.out.println("OpenClose encountered IO issue :" + ioe);
                  fail = true;
              } finally {
                  if (fd.valid()) { // fd should not be valid after first close() call
                      System.out.println("OpenClose: FileDescriptor shouldn't be valid");
                      fail = true;
                  }
                  done.countDown();
              }
          }
     }

     private static class BadFileInputStream extends FileInputStream {

         BadFileInputStream(FileDescriptor fd) {
             super(fd);
         }

         public void close() throws IOException {
             throw new IOException("Bad close operation");
         }
     }

     private static class BadFileOutputStream extends FileOutputStream {

         BadFileOutputStream(FileDescriptor fd) {
             super(fd);
         }

         public void close() throws IOException {
             throw new IOException("Bad close operation");
         }
     }

 }
	/*
	* Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	/*
	* @test
	* @bug 7105952 6322678 7082769
	* @summary Improve finalisation for FileInputStream/FileOutputStream/RandomAccessFile
	* @run main/othervm Sharing
	*/

	import java.io.*;
	import java.nio.channels.FileChannel;
	import java.nio.channels.FileLock;
	import java.util.concurrent.CountDownLatch;

	public class Sharing {

	final static int numFiles = 10;
	volatile static boolean fail;

	public static void main(String[] args) throws Exception {
	TestFinalizer();
	TestMultipleFD();
	TestIsValid();
	MultiThreadedFD();
	TestCloseAll();
	}

	/**
	* Finalizer shouldn't discard a file descriptor until all streams have
	* finished with it.
	*/
	private static void TestFinalizer() throws Exception {
	FileDescriptor fd = null;
	File tempFile = new File("TestFinalizer1.txt");
	tempFile.deleteOnExit();
	try (Writer writer = new FileWriter(tempFile)) {
	for (int i=0; i<5; i++) {
	writer.write("test file content test file content");
	}
	}

	FileInputStream fis1 = new FileInputStream(tempFile);
	fd = fis1.getFD();
	// Create a new FIS based on the existing FD (so the two FIS's share the same native fd)
	try (FileInputStream fis2 = new FileInputStream(fd)) {
	// allow fis1 to be gc'ed
	fis1 = null;
	int ret = 0;
	while(ret >= 0) {
	// encourage gc
	System.gc();
	// read from fis2 - when fis1 is gc'ed and finalizer is run, read will fail
	System.out.print(".");
	ret = fis2.read();
	}
	}

	// variation of above. Use RandomAccessFile to obtain a filedescriptor
	File testFinalizerFile = new File("TestFinalizer");
	RandomAccessFile raf = new RandomAccessFile(testFinalizerFile, "rw");
	raf.writeBytes("test file content test file content");
	raf.seek(0L);
	fd = raf.getFD();
	try (FileInputStream fis3 = new FileInputStream(fd)) {
	// allow raf to be gc'ed
	raf = null;
	int ret = 0;
	while (ret >= 0) {
	// encourage gc
	System.gc();
	/*
	* read from fis3 - when raf is gc'ed and finalizer is run,
	* fd should still be valid.
	*/
	System.out.print(".");
	ret = fis3.read();
	}
	} finally {
	testFinalizerFile.delete();
	}
	}

	/**
	* Exercise FileDispatcher close()/preClose()
	*/
	private static void TestMultipleFD() throws Exception {
	RandomAccessFile raf = null;
	FileOutputStream fos = null;
	FileInputStream fis = null;
	FileChannel fc = null;
	FileLock fileLock = null;

	File test1 = new File("test1");
	try {
	raf = new RandomAccessFile(test1, "rw");
	fos = new FileOutputStream(raf.getFD());
	fis = new FileInputStream(raf.getFD());
	fc = raf.getChannel();
	fileLock = fc.lock();
	raf.setLength(0L);
	fos.flush();
	fos.write("TEST".getBytes());
	} finally {
	if (fileLock != null) fileLock.release();
	if (fis != null) fis.close();
	if (fos != null) fos.close();
	if (raf != null) raf.close();
	test1.delete();
	}

	/*
	* Close out in different order to ensure FD is not
	* closed out too early
	*/
	File test2 = new File("test2");
	try {
	raf = new RandomAccessFile(test2, "rw");
	fos = new FileOutputStream(raf.getFD());
	fis = new FileInputStream(raf.getFD());
	fc = raf.getChannel();
	fileLock = fc.lock();
	raf.setLength(0L);
	fos.flush();
	fos.write("TEST".getBytes());
	} finally {
	if (fileLock != null) fileLock.release();
	if (raf != null) raf.close();
	if (fos != null) fos.close();
	if (fis != null) fis.close();
	test2.delete();
	}

	// one more time, fos first this time
	File test3 = new File("test3");
	try {
	raf = new RandomAccessFile(test3, "rw");
	fos = new FileOutputStream(raf.getFD());
	fis = new FileInputStream(raf.getFD());
	fc = raf.getChannel();
	fileLock = fc.lock();
	raf.setLength(0L);
	fos.flush();
	fos.write("TEST".getBytes());
	} finally {
	if (fileLock != null) fileLock.release();
	if (fos != null) fos.close();
	if (raf != null) raf.close();
	if (fis != null) fis.close();
	test3.delete();
	}
	}

	/**
	* Similar to TestMultipleFD() but this time we
	* just get and use FileDescriptor.valid() for testing.
	*/
	private static void TestIsValid() throws Exception {
	FileDescriptor fd = null;
	RandomAccessFile raf = null;
	FileOutputStream fos = null;
	FileInputStream fis = null;
	FileChannel fc = null;

	File test1 = new File("test1");
	try {
	raf = new RandomAccessFile(test1, "rw");
	fd = raf.getFD();
	fos = new FileOutputStream(fd);
	fis = new FileInputStream(fd);
	} finally {
	try {
	if (fis != null) fis.close();
	if (fd.valid()) {
	throw new RuntimeException("[FIS close()] FileDescriptor shouldn't be valid");
	}
	if (fos != null) fos.close();
	if (raf != null) raf.close();
	} finally {
	test1.delete();
	}
	}

	/*
	* Close out in different order to ensure FD is
	* closed correctly.
	*/
	File test2 = new File("test2");
	try {
	raf = new RandomAccessFile(test2, "rw");
	fd = raf.getFD();
	fos = new FileOutputStream(fd);
	fis = new FileInputStream(fd);
	} finally {
	try {
	if (raf != null) raf.close();
	if (fd.valid()) {
	throw new RuntimeException("[RAF close()] FileDescriptor shouldn't be valid");
	}
	if (fos != null) fos.close();
	if (fis != null) fis.close();
	} finally {
	test2.delete();
	}
	}

	// one more time, fos first this time
	File test3 = new File("test3");
	try {
	raf = new RandomAccessFile(test3, "rw");
	fd = raf.getFD();
	fos = new FileOutputStream(fd);
	fis = new FileInputStream(fd);
	} finally {
	try {
	if (fos != null) fos.close();
	if (fd.valid()) {
	throw new RuntimeException("[FOS close()] FileDescriptor shouldn't be valid");
	}
	if (raf != null) raf.close();
	if (fis != null) fis.close();
	} finally {
	test3.delete();
	}
	}
	}

	/**
	* Test concurrent access to the same FileDescriptor
	*/
	private static void MultiThreadedFD() throws Exception {
	RandomAccessFile raf = null;
	FileDescriptor fd = null;
	int numThreads = 2;
	CountDownLatch done = new CountDownLatch(numThreads);
	OpenClose[] fileOpenClose = new OpenClose[numThreads];
	File MultipleThreadedFD = new File("MultipleThreadedFD");
	try {
	raf = new RandomAccessFile(MultipleThreadedFD, "rw");
	fd = raf.getFD();
	for(int count=0;count<numThreads;count++) {
	fileOpenClose[count] = new OpenClose(fd, done);
	fileOpenClose[count].start();
	}
	done.await();
	} finally {
	try {
	if(raf != null) raf.close();
	// fd should now no longer be valid
	if(fd.valid()) {
	throw new RuntimeException("FileDescriptor should not be valid");
	}
	// OpenClose thread tests failed
	if(fail) {
	throw new RuntimeException("OpenClose thread tests failed.");
	}
	} finally {
	MultipleThreadedFD.delete();
	}
	}
	}

	/**
	* Test closeAll handling in FileDescriptor
	*/
	private static void TestCloseAll() throws Exception {
	File testFile = new File("test");
	testFile.deleteOnExit();
	RandomAccessFile raf = new RandomAccessFile(testFile, "rw");
	FileInputStream fis = new FileInputStream(raf.getFD());
	fis.close();
	if (raf.getFD().valid()) {
	throw new RuntimeException("FD should not be valid.");
	}

	// Test the suppressed exception handling - FileInputStream

	raf = new RandomAccessFile(testFile, "rw");
	fis = new FileInputStream(raf.getFD());
	BadFileInputStream bfis1 = new BadFileInputStream(raf.getFD());
	BadFileInputStream bfis2 = new BadFileInputStream(raf.getFD());
	BadFileInputStream bfis3 = new BadFileInputStream(raf.getFD());
	// extra test - set bfis3 to null
	bfis3 = null;
	try {
	fis.close();
	} catch (IOException ioe) {
	ioe.printStackTrace();
	if (ioe.getSuppressed().length != 2) {
	throw new RuntimeException("[FIS]Incorrect number of suppressed " +
	"exceptions received : " + ioe.getSuppressed().length);
	}
	}
	if (raf.getFD().valid()) {
	// we should still have closed the FD
	// even with the exception.
	throw new RuntimeException("[FIS]TestCloseAll : FD still valid.");
	}

	// Now test with FileOutputStream

	raf = new RandomAccessFile(testFile, "rw");
	FileOutputStream fos = new FileOutputStream(raf.getFD());
	BadFileOutputStream bfos1 = new BadFileOutputStream(raf.getFD());
	BadFileOutputStream bfos2 = new BadFileOutputStream(raf.getFD());
	BadFileOutputStream bfos3 = new BadFileOutputStream(raf.getFD());
	// extra test - set bfos3 to null
	bfos3 = null;
	try {
	fos.close();
	} catch (IOException ioe) {
	ioe.printStackTrace();
	if (ioe.getSuppressed().length != 2) {
	throw new RuntimeException("[FOS]Incorrect number of suppressed " +
	"exceptions received : " + ioe.getSuppressed().length);
	}
	}
	if (raf.getFD().valid()) {
	// we should still have closed the FD
	// even with the exception.
	throw new RuntimeException("[FOS]TestCloseAll : FD still valid.");
	}
	}

	/**
	* A thread which will open and close a number of FileInputStreams and
	* FileOutputStreams referencing the same native file descriptor.
	*/
	private static class OpenClose extends Thread {
	private FileDescriptor fd = null;
	private CountDownLatch done;
	FileInputStream[] fisArray = new FileInputStream[numFiles];
	FileOutputStream[] fosArray = new FileOutputStream[numFiles];

	OpenClose(FileDescriptor filedescriptor, CountDownLatch done) {
	this.fd = filedescriptor;
	this.done = done;
	}

	public void run() {
	try {
	for(int i=0;i<numFiles;i++) {
	fisArray[i] = new FileInputStream(fd);
	fosArray[i] = new FileOutputStream(fd);
	}

	// Now close out
	for(int i=0;i<numFiles;i++) {
	if(fisArray[i] != null) fisArray[i].close();
	if(fosArray[i] != null) fosArray[i].close();
	}

	} catch(IOException ioe) {
	System.out.println("OpenClose encountered IO issue :" + ioe);
	fail = true;
	} finally {
	if (fd.valid()) { // fd should not be valid after first close() call
	System.out.println("OpenClose: FileDescriptor shouldn't be valid");
	fail = true;
	}
	done.countDown();
	}
	}
	}

	private static class BadFileInputStream extends FileInputStream {

	BadFileInputStream(FileDescriptor fd) {
	super(fd);
	}

	public void close() throws IOException {
	throw new IOException("Bad close operation");
	}
	}

	private static class BadFileOutputStream extends FileOutputStream {

	BadFileOutputStream(FileDescriptor fd) {
	super(fd);
	}

	public void close() throws IOException {
	throw new IOException("Bad close operation");
	}
	}

	}