(An open source PDF reader source code, a lot of code, you can look at if you are interested.
AndroidPdfViewer\activitysrc\net\sf\andpdf\pdfviewer\ByteBuffer.java
AndroidPdfViewer\activitysrc\net\sf\andpdf\pdfviewer\MyAdapter.java
AndroidPdfViewer\activitysrc\net\sf\andpdf\pdfviewer\PdfFileSelectActivity.java
AndroidPdfViewer\activitysrc\net\sf\andpdf\pdfviewer\PdfViewerActivity.java
AndroidPdfViewer\activitysrc\net\sf\andpdf\pdfviewer\SimplePersistence.java
AndroidPdfViewer\bin\androswing\tree\DefaultMutableTreeNode.class
AndroidPdfViewer\bin\com\sun\pdfview\action\GoToAction.class
AndroidPdfViewer\bin\com\sun\pdfview\action\PDFAction.class
AndroidPdfViewer\bin\com\sun\pdfview\colorspace\GrayColorSpace.class
AndroidPdfViewer\bin\com\sun\pdfview\colorspace\IndexedColor.class
AndroidPdfViewer\bin\com\sun\pdfview\colorspace\PDFColorSpace.class
AndroidPdfViewer\bin\com\sun\pdfview\colorspace\RGBColorSpace.class
AndroidPdfViewer\bin\com\sun\pdfview\decode\ASCII85Decode.class
AndroidPdfViewer\bin\com\sun\pdfview\decode\ASCIIHexDecode.class
AndroidPdfViewer\bin\com\sun\pdfview\decode\CCITTCodes
AndroidPdfViewer\bin\com\sun\pdfview\decode\CCITTFaxDecode.class
AndroidPdfViewer\bin\com\sun\pdfview\decode\CCITTFaxDecoder.class
AndroidPdfViewer\bin\com\sun\pdfview\decode\DCTDecode.class
AndroidPdfViewer\bin\com\sun\pdfview\decode\FlateDecode.class
AndroidPdfViewer\bin\com\sun\pdfview\decode\LZWDecode.class
AndroidPdfViewer\bin\com\sun\pdfview\decode\PDFDecoder.class
AndroidPdfViewer\bin\com\sun\pdfview\decode\PNGPredictor.class
AndroidPdfViewer\bin\com\sun\pdfview\decode\Predictor.class
AndroidPdfViewer\bin\com\sun\pdfview\decode\RunLengthDecode.class
AndroidPdfViewer\bin\com\sun\pdfview\decrypt\CryptFilterDecrypter.class
AndroidPdfViewer\bin\com\sun\pdfview\decrypt\EncryptionUnsupportedByPlatformException.class
AndroidPdfViewer\bin\com\sun\pdfview\decrypt\EncryptionUnsupportedByProductException.class
AndroidPdfViewer\bin\com\sun\pdfview\decrypt\IdentityDecrypter.class
AndroidPdfViewer\bin\com\sun\pdfview\decrypt\PDFAuthenticationFailureException.class
AndroidPdfViewer\bin\com\sun\pdfview\decrypt\PDFDecrypter.class
..... Too many files omitted)