1. Java @Ch19. Binary I/O 2011.05.06

2. Outline Text I/O Chap 9. WriteData Chap 9. ReadData Binary I/O Text I/O vs Binary I/O Binary I/O Classes Using DataInputStream/DataOutputStream Copy File [Sample code] TestFileStream.java 、 TestDataStream.java 、 Copy.java

3. Text I/O Write: // Write text to a file named temp.txt PrintWriter output = new PrintWriter(“temp.txt”); // Invoke the print method from the object to write a string into a file. Output.print(“Java 101”) // Closed the file. Output.close();

4. Read: // Using Scanner class Scanner input = new Scanner(new File(“temp.txt”)); System.out.println(input.nextLine()); // input.nextLine() 回傳 “Java 101”

5. Chap 9. WriteData

6. Chap 9. ReadData

7. Binary I/O All files are store in binary format. No need to encode and decode.

8. Binary I/O Program Input object created from an input class Output object created from an output class File 01011…1001 11001…1011 Input stream output stream The program receives data and send data

9. Text I/O vs Binary I/O Text I/O program The Unicode of the character e.g.,”199” The encoding of the character is stored in the file 00110001 00111001 00111001 Encoding Decoding Binary I/O program A byte is read/written e.g.,”199” The encoding of the character is stored in the file 00110111 ※ Text I/O requires encoding and decoding, whereas binary I/O does not ※ 199 = 12 x16 + 7  0xC7 1

10. Binary I/O Classes 課本 P.676

11. 程式範例 :  TestFileStream.java

12. Using DataInputStream/DataOutputStream Data streams constructors: public DataInputStream(InputStream instream) public DataOutputStream(OutputStream outstream) Create data streams: DataInputStream input = new DataInputStream(new FileInputStream(“in.dat”)); DataOutputStream output = new DataOutputStream(new FileOutputStream(“out.dat”));

13. 程式範例 :  TestDataStream.java

14. BufferedInputStream/BufferedOutputStream BufferedInputStream/BufferedOutputStream can be used to speed up input and output by reducing number of reads and writes. All the methods in BufferedInputStream/BufferedOutputStream are inherited from the InputStream/OutputStream classes

15. 可在 TestDataStream.java 的第 8 行及第 22 行加入 : DataOutputStream output = new DataOutputStream(new BufferedOutputStream(new FileOutputStream("temp.dat"))); DataInputStream input = new DataInputStream(new BufferedInputStream(new FileInputStream("temp.dat")));

16. Copy File 程式範例 :  Copy.java ※ Java Copy source target

17. 程式練習 :  Programming Exercises 19.2