Download as PDF, PPTX
![marcello.thiry@gmail.com read() reads a single byte read(byte[] b) reads b.length bytes into an array read(byte[] b, int off, int len) reads len bytes into an array, starting from the position off skip(long n) skips discards n bytes close() closes the stream https://docs.oracle.com/javase/8/docs/api/java/io/InputStream.html](https://image.slidesharecdn.com/slides-oo-java-151203014118-lva1-app6891/75/java-io-streams-and-files-22-2048.jpg)
![marcello.thiry@gmail.com write(int b) writes a single byte write(byte[] b) writes b.length bytes from the array write(byte[] b, int off, int len) writes len bytes from the array starting at offset off flush() forces any buffered output bytes to be written out](https://image.slidesharecdn.com/slides-oo-java-151203014118-lva1-app6891/75/java-io-streams-and-files-24-2048.jpg)
![marcello.thiry@gmail.com String fileName = "c:/temp/file.exe"; int byteValue; try { InputStream in = new FileInputStream(fileName); while ((byteValue = in.read()) != -1) { System.out.format("[%2X]n", byteValue); } in.close(); } catch (IOException ex) {...}](https://image.slidesharecdn.com/slides-oo-java-151203014118-lva1-app6891/75/java-io-streams-and-files-27-2048.jpg)
![marcello.thiry@gmail.com String fileName = "c:/temp/file.exe"; int byteValue; try { InputStream in = new FileInputStream(fileName); while ((byteValue = in.read()) != -1) { System.out.format("[%2X]n", byteValue); } in.close(); } catch (IOException ex) {...}](https://image.slidesharecdn.com/slides-oo-java-151203014118-lva1-app6891/75/java-io-streams-and-files-28-2048.jpg)
![marcello.thiry@gmail.com Try-with-resources String fileName = "c:/temp/file.exe"; byte[] bytes = new byte[500]; int read; try { try (InputStream in = new FileInputStream(fileName)) { while ((read = in.read(bytes)) != -1) { System.out.format("%d bytes read:n", read); for (int i = 0; i < read; i++) { System.out.format("[%2X]", bytes[i]); } System.out.println(); } } } catch (IOException ex) {...}](https://image.slidesharecdn.com/slides-oo-java-151203014118-lva1-app6891/75/java-io-streams-and-files-30-2048.jpg)
![marcello.thiry@gmail.com Try-with-resources String fileName = "c:/temp/file.exe"; byte[] bytes = new byte[500]; int read; try { try (InputStream in = new FileInputStream(fileName)) { while ((read = in.read(bytes)) != -1) { System.out.format("%d bytes read:n", read); for (int i = 0; i < read; i++) { System.out.format("[%2X]", bytes[i]); } System.out.println(); } } } catch (IOException ex) {...}](https://image.slidesharecdn.com/slides-oo-java-151203014118-lva1-app6891/75/java-io-streams-and-files-31-2048.jpg)
![marcello.thiry@gmail.com String fileName = "d:/downloads/mynewfile.txt"; try { try (OutputStream out = new FileOutputStream(fileName)) { byte[] bytes = new byte[]{'T', 'E', 'S', 'T', 32, 0x41}; out.write(bytes); } } catch (IOException e) {...}](https://image.slidesharecdn.com/slides-oo-java-151203014118-lva1-app6891/75/java-io-streams-and-files-35-2048.jpg)
![marcello.thiry@gmail.com class Reader Abstract class for reading character streams read(): reads a single character read(char[]): reads characters into an array skip(long): skips N characters close(): closes the stream https://docs.oracle.com/javase/8/docs/api/java/io/Reader.html](https://image.slidesharecdn.com/slides-oo-java-151203014118-lva1-app6891/75/java-io-streams-and-files-45-2048.jpg)
![marcello.thiry@gmail.com class Writer Abstract class for writing to character streams write(int): writes a single character write(char[]): writes an array of characters write(String): writes a string close(): closes the stream https://docs.oracle.com/javase/8/docs/api/java/io/Writer.html](https://image.slidesharecdn.com/slides-oo-java-151203014118-lva1-app6891/75/java-io-streams-and-files-60-2048.jpg)
Uploaded byMarcello Thiry
java.io - streams and files
The document provides a comprehensive guide on handling streams and files in Java, including fundamental concepts such as character sets, encoding, and serialization. It includes practical examples of reading and writing both binary and text files using various Java classes like InputStream, OutputStream, FileReader, and FileWriter. Additionally, it covers handling exceptions and the importance of using try-with-resources for better resource management.
In this document
Powered by AI
Introduction to Java I/O, covering streams and files, glossary terms, and the basics of the course.
Explains character sets like ASCII, UNICODE, encoding types, and their relevance to programming.
Defines streams in Java, including data elements (bytes, characters), and data buffers.
Discusses object serialization methods in Java and what constitutes an Application Programming Interface (API).
Details on how Java handles streams, inputs/outputs, and typical applications in file reading/writing.
Describes methods for reading data from input streams, including practical examples and error handling.
Focuses on writing data to output streams, demonstrating file writing methods and object serialization.
Explains reading and writing text files using Reader and Writer classes, including handling UNICODE.
Provides additional readings and resources for Java I/O programming.
java.io - streams and files
- 1. marcello.thiry@gmail.comPackage java.io: streamsand files http://3.bp.blogspot.com/- Eg1r_jQcFFk/UcAVENEyKYI/AAAA AAAAADc/5fgJlvZUlp4/s1600/sr22 -file-and-filing-cabinet.jpg Supplementary material
- 2. marcello.thiry@gmail.com http://ideas.scup.com/pt/files/2013/06/conte%C3%BAdo.jpg 1. Basicglossary 2. Streams and files in Java (reading and writing) 3. Text files in Java (reading and writing) Contents.
- 3.
- 4. marcello.thiry@gmail.com if you donot know much about charsets, code pages, encoding, ASCII, UNICODE, etc. Before we start… Take a look in this article http://www.joelonsoftware.com/articles/Unicode.html The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!) by Joel Spolsky It’s a bit old, but a good start
- 5. marcello.thiry@gmail.com Set of charactersyou can use Charset Repertoire ISO-8859-1 - Western Alphabet ISO-8859-5 - Cyrillic Alphabet JIS X 0208 - Japanese Alphabet ISO-8859-7 - Greek Alphabet
- 6. marcello.thiry@gmail.com A numerical valueassigned to each character in a character set repertoire Can be represented by one or more bytes Code Point Code Position
- 7. marcello.thiry@gmail.com Code Point CodePosition A = 41hex (ASCII) a = 61hex (ASCII) A = 00hex 41hex (UNICODE) = 33hex 34hex (UNICODE) a = 00hex 61hex (UNICODE) = 42hex F4hex (UNICODE)
- 8. A coded characterset* *Sometimes called code page UNICODE
- 9. marcello.thiry@gmail.com The way algorithmthe coded characters are stored into memory Character Encoding UTF-8 UTF-16 UTF-32
- 10.
- 11. marcello.thiry@gmail.com Sequence of dataelements made available over time Stream
- 12. marcello.thiry@gmail.com Which data elements? Byteraw binary data Character Primitive data type Object Stream
- 13. marcello.thiry@gmail.com A continuous streamof bytes stored in a file system Stream File http://ebiznet2u.com/wp-content/uploads/2012/07/file-viewer.jpg
- 14. marcello.thiry@gmail.com Region of aphysical memory storage used to temporarily store data while it is being moved from one place to another Data Buffer
- 15. marcello.thiry@gmail.com Conversion of anobject to a series of bytes, which lets a program write whole objects out to streams and read them back again Object Serialization
- 16. Set of routines,protocols, and tools to access a software component/module without the need to know details of its implementation Application Programming* Interface API *Also used: program
- 17.
- 18. marcello.thiry@gmail.com Bytes Characters automatically translatesto and from the local character set Data primitive data type and String values Objects What is a stream in Java? handle I/O of
- 19. marcello.thiry@gmail.com Optimizes input andoutput by reducing the number of calls to the native API And a buffered stream?
- 20. marcello.thiry@gmail.com Where to use? Files Networkconnections sockets Blob database fields System.in standard input System.out standard output … To write/read into/from
- 21.
- 22. marcello.thiry@gmail.com read() reads asingle byte read(byte[] b) reads b.length bytes into an array read(byte[] b, int off, int len) reads len bytes into an array, starting from the position off skip(long n) skips discards n bytes close() closes the stream https://docs.oracle.com/javase/8/docs/api/java/io/InputStream.html
- 23. marcello.thiry@gmail.com mark(int readlimit) marksthe current position in this input stream reset() repositions this stream to the position at the time the mark method was last called https://docs.oracle.com/javase/8/docs/api/java/io/InputStream.html And, if markSupported()...
- 24. marcello.thiry@gmail.com write(int b) writesa single byte write(byte[] b) writes b.length bytes from the array write(byte[] b, int off, int len) writes len bytes from the array starting at offset off flush() forces any buffered output bytes to be written out
- 25.
- 26. marcello.thiry@gmail.com Input stream for readingBYTES from a FILE Binary files UNICODE files https://docs.oracle.com/javase/8/docs/api/java/io/FileInputStream.html
- 27. marcello.thiry@gmail.com String fileName ="c:/temp/file.exe"; int byteValue; try { InputStream in = new FileInputStream(fileName); while ((byteValue = in.read()) != -1) { System.out.format("[%2X]n", byteValue); } in.close(); } catch (IOException ex) {...}
- 28. marcello.thiry@gmail.com String fileName ="c:/temp/file.exe"; int byteValue; try { InputStream in = new FileInputStream(fileName); while ((byteValue = in.read()) != -1) { System.out.format("[%2X]n", byteValue); } in.close(); } catch (IOException ex) {...}
- 29. marcello.thiry@gmail.com FileNotFoundException For constructors thatuse a file name as an argument If the named file does not exist, is a directory rather than a regular file, or for some other reason cannot be opened for reading
- 30. marcello.thiry@gmail.com Try-with-resources String fileName ="c:/temp/file.exe"; byte[] bytes = new byte[500]; int read; try { try (InputStream in = new FileInputStream(fileName)) { while ((read = in.read(bytes)) != -1) { System.out.format("%d bytes read:n", read); for (int i = 0; i < read; i++) { System.out.format("[%2X]", bytes[i]); } System.out.println(); } } } catch (IOException ex) {...}
- 31. marcello.thiry@gmail.com Try-with-resources String fileName ="c:/temp/file.exe"; byte[] bytes = new byte[500]; int read; try { try (InputStream in = new FileInputStream(fileName)) { while ((read = in.read(bytes)) != -1) { System.out.format("%d bytes read:n", read); for (int i = 0; i < read; i++) { System.out.format("[%2X]", bytes[i]); } System.out.println(); } } } catch (IOException ex) {...}
- 32. marcello.thiry@gmail.com From this pointforward, all our examples will use the Try-with-resources statement
- 33.
- 34. marcello.thiry@gmail.com Output stream for writing BYTESto a FILE Binary files UNICODE files https://docs.oracle.com/javase/8/docs/api/java/io/FileOutputStream.html
- 35. marcello.thiry@gmail.com String fileName ="d:/downloads/mynewfile.txt"; try { try (OutputStream out = new FileOutputStream(fileName)) { byte[] bytes = new byte[]{'T', 'E', 'S', 'T', 32, 0x41}; out.write(bytes); } } catch (IOException e) {...}
- 36. marcello.thiry@gmail.com And if Iwant to write or read objects from a stream?
- 37.
- 38.
- 39.
- 40. marcello.thiry@gmail.com try (ObjectOutputStream out= new ObjectOutputStream(new FileOutputStream("user.dat"))) { out.writeObject(new User("a", "a")); out.writeObject(new User("b", "b")); out.writeObject(new User("c", "c")); out.flush(); } catch (IOException e) {...} User u; try (ObjectInputStream in = new ObjectInputStream(new FileInputStream("user.dat"))) { for (int i = 0; i < 3; i++) { u = (User) in.readObject(); System.out.println(u.getLogin() + ", " + u.getPassword()); } } catch (IOException | ClassNotFoundException e) {...}
- 41.
- 42.
- 43.
- 44.
- 45. marcello.thiry@gmail.com class Reader Abstract classfor reading character streams read(): reads a single character read(char[]): reads characters into an array skip(long): skips N characters close(): closes the stream https://docs.oracle.com/javase/8/docs/api/java/io/Reader.html
- 46. marcello.thiry@gmail.com class FileReader Reads characterfiles Default character encoding Default byte-buffer size https://docs.oracle.com/javase/8/docs/api/java/io/FileReader.html
- 47. marcello.thiry@gmail.com String fileName ="temp.txt"; String line; FileReader fileReader = new FileReader(fileName);
- 48. marcello.thiry@gmail.com class BufferedReader Usually wrapsFileReader to improve efficiency https://docs.oracle.com/javase/8/docs/api/java/io/BufferedReader.html Buffer size may be specified Reading of characters, arrays, and lines
- 49. marcello.thiry@gmail.com String fileName ="temp.txt"; String line; FileReader fileReader = new FileReader(fileName); try (BufferedReader bufferedReader = new BufferedReader(fileReader)) { while ((line = bufferedReader.readLine()) != null) { System.out.println(line); } }
- 50. marcello.thiry@gmail.com String fileName ="temp.txt"; String line; FileReader fileReader = new FileReader(fileName); try (BufferedReader bufferedReader = new BufferedReader(fileReader)) { while ((line = bufferedReader.readLine()) != null) { System.out.println(line); } }
- 51. marcello.thiry@gmail.com String fileName ="temp.txt"; String line; FileReader fileReader = new FileReader(fileName); try (BufferedReader bufferedReader = new BufferedReader(fileReader)) { while ((line = bufferedReader.readLine()) != null) { System.out.println(line); } }
- 52. marcello.thiry@gmail.com String fileName ="temp.txt"; String line; FileReader fileReader = new FileReader(fileName); try (BufferedReader bufferedReader = new BufferedReader(fileReader)) { while ((line = bufferedReader.readLine()) != null) { System.out.println(line); } }
- 53. marcello.thiry@gmail.com String fileName =“temp.txt"; String line; try { FileReader fileReader = new FileReader(fileName); try (BufferedReader bufferedReader = new BufferedReader(fileReader)) { while ((line = bufferedReader.readLine()) != null) { System.out.println(line); } } } catch (FileNotFoundException ex) {... } catch (IOException ex) {... }
- 54. marcello.thiry@gmail.com But what aboutthe class InputStreamReader? https://docs.oracle.com/javase/8/docs/api/java/io/InputStreamReader.html Reads bytes and decodes them into characters using a specified charset Bridge from byte streams to character streams
- 55. marcello.thiry@gmail.com class InputStreamReader https://docs.oracle.com/javase/8/docs/api/java/io/InputStreamReader.html For topefficiency, consider wrapping within a BufferedReader
- 56. marcello.thiry@gmail.com String line; try { InputStreamReaderinputReader = new InputStreamReader(System.in); try (BufferedReader bufferedReader = new BufferedReader(inputReader)) { while (!"".equals(line = bufferedReader.readLine())) { System.out.println(line); } } } catch (IOException e) {...}
- 57. marcello.thiry@gmail.com Now we canuse FileInputStream e InputStreamReader to read a UNICODE file
- 58. marcello.thiry@gmail.com try { FileInputStream in= new FileInputStream("c:/temp/fileUTF16.txt"); InputStreamReader inReader = new InputStreamReader(in, "UTF-16"); try (BufferedReader buffReader = new BufferedReader(inReader)) { int character; while ((character = buffReader.read()) != -1) { System.out.print((char) character); } } } catch (IOException e) {...}
- 59.
- 60. marcello.thiry@gmail.com class Writer Abstract classfor writing to character streams write(int): writes a single character write(char[]): writes an array of characters write(String): writes a string close(): closes the stream https://docs.oracle.com/javase/8/docs/api/java/io/Writer.html
- 61. marcello.thiry@gmail.com class FileWriter Writes incharacter files Default character encoding Default byte-buffer size https://docs.oracle.com/javase/8/docs/api/java/io/FileWriter.html
- 62. marcello.thiry@gmail.com String fileName =“temp.txt"; FileWriter fileWriter = new FileWriter(fileName); FileWriter fileWriter = new FileWriter(fileName, false); FileWriter fileWriter = new FileWriter(fileName, true);
- 63. marcello.thiry@gmail.com String fileName ="c:/temp.txt"; try { try (FileWriter fileWriter = new FileWriter(fileName)) { fileWriter.write("My first line"); fileWriter.write("rn"); // new line - windows fileWriter.write("My second line"); } } catch (IOException e) {...}
- 64. marcello.thiry@gmail.com class BufferedWriter Usually wrapsFileWriter to improve efficiency https://docs.oracle.com/javase/8/docs/api/java/io/BufferedWriter.html Buffer size may be specified Writing characters, arrays, and lines
- 65. marcello.thiry@gmail.com String fileName ="c:/temp/MyFile.txt"; try { FileWriter writer = new FileWriter(fileName, true); try (BufferedWriter buffWriter = new BufferedWriter(writer)) { buffWriter.write("My first line"); buffWriter.newLine(); buffWriter.write("My second line!"); } } catch (IOException e) {...}
- 66. marcello.thiry@gmail.com But what aboutthe class OutputStreamWriter? https://docs.oracle.com/javase/8/docs/api/java/io/OutputStreamWriter.html Characters written to it are encoded into bytes using a specified charset bridge from character to byte streams
- 67. marcello.thiry@gmail.com class OutputStreamWriter For topefficiency, consider wrapping within a BufferedWriter https://docs.oracle.com/javase/8/docs/api/java/io/OutputStreamWriter.html
- 68. marcello.thiry@gmail.com try { OutputStreamWriter outWriter= new OutputStreamWriter(System.out); try (BufferedWriter buffWriter = new BufferedWriter(outWriter)) { buffWriter.write("Printing a line on the console"); buffWriter.newLine(); buffWriter.write("Printing a second line...rn"); } } catch (IOException e) {}
- 69. marcello.thiry@gmail.com Now we canuse FileOutputStream e OutputStreamWriter to write into a UNICODE file
- 70. marcello.thiry@gmail.com String fileName ="c:/temp/MyNewFile.txt"; try { FileOutputStream out = new FileOutputStream(fileName); OutputStreamWriter outWriter = new OutputStreamWriter(out, "UTF-16"); try (BufferedWriter buffWriter = new BufferedWriter(outWriter)) { buffWriter.write("UNICODE text"); buffWriter.newLine(); buffWriter.write("Some more..."); } } catch (IOException e) {...}
- 71. marcello.thiry@gmail.com References. Java™ Platform,Standard Edition 8 API Specification. https://docs.oracle.com/javase/8/docs/api/overview-summary.html. The Java™ Tutorials. https://docs.oracle.com/javase/tutorial/.