输入和输出Java代码 1. // Stream, Reader, Writer 2. Stream: 处 理字节流 3. Reader/Writer: 处理字符，通用Unicode 4. 5. // 从标准输入设备读数据 6. 1. 用System.in的BufferedInputStream()读取字节 7. int b = System.in.read(); 8. System.out.println("Read data: " + (char)b); // 强 制转换为字符 9. 2. BufferedReader 读取文本 10. 如果从Stream转成Reader，使用 InputStreamReader类 11. BufferedReader is = new BufferedReader(new 12. InputStreamReader(System.in)); 13. String inputLine; 14. while ((inputLine = is.readLine()) != null) { 15. System.out.println(inputLine); 16. int val = Integer.parseInt(inputLine); // 如果inputLine为整数 17. } 18. is.close(); 19. 20. // 向标准输出设备写数据 21. 1. 用System.out的println()打印数据 22. 2. 用PrintWriter打印 23. PrintWriter pw = new PrintWriter(System.out); 24. pw.println("The answer is " + myAnswer + " at this time."); 25. 26. // Formatter类 27. 格 式化打印内容 28. Formatter fmtr = new Formatter(); 29. fmtr.format("%1$04d - the year of %2$f", 1951, Math.PI); 30. 或 者System.out.printf();或者System.out.format(); 31. 32. // 原始扫描 33. void doFile(Reader is) { 34. int c; 35. while ((c = is.read()) != -1) { 36. System.out.println((char)c); 37. } 38. } 39. 40. // Scanner扫描 41. Scanner 可以读取File, InputStream, String, Readable 42. try { 43. Scanner scan = new Scanner(new File("a.txt")); 44. while (scan.hasNext()) { 45. String s = scan.next(); 46. } 47. } catch (FileNotFoundException e) { 48. e.printStackTrace(); 49. } 50. } 51. 52. // 读取文件 53. BufferedReader is = new BufferedReader(new FileReader("myFile.txt")); 54. BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("bytes.bat")); 55. is.close(); 56. bos.close(); 57. 58. // 复制文件 59. BufferedIutputStream is = new BufferedIutputStream(new FileIutputStream("oldFile.txt")); 60. BufferedOutputStream os = new BufferedOutputStream(new FileOutputStream("newFile.txt")); 61. int b; 62. while ((b = is.read()) != -1) { 63. os.write(b); 64. } 65. is.close(); 66. os.close(); 67. 68. // 文件读入字符串 69. StringBuffer sb = new StringBuffer(); 70. char[] b = new char[8192]; 71. int n; 72. // 读一个块，如果有字符，加入缓冲区 73. while ((n = is.read(b)) > 0) { 74. sb.append(b, 0, n); 75. } 76. return sb.toString(); 77. 78. // 重定向标准流 79. String logfile = "error.log"; 80. System.setErr(new PrintStream(new FileOutputStream(logfile))); 81. 82. // 读写不同字符集文本 83. BufferedReader chinese = new BufferedReader(new InputStreamReader(new FileInputStream("chinese.txt"), "ISO8859_1")); 84. PrintWriter standard = new PrintWriter(new OutputStreamWriter(new FileOutputStream("standard.txt"), "UTF-8")); 85. 86. // 读取二进制数据 87. DataOutputStream os = new DataOutputStream(new FileOutputStream("a.txt")); 88. os.writeInt(i); 89. os.writeDouble(d); 90. os.close(); 91. 92. // 从指定位置读数据 93. RandomAccessFile raf = new RandomAccessFile(fileName, "r"); // r表示已 只读打开 94. raf.seek(15); // 从15开始读 95. raf.readInt(); 96. raf.radLine(); 97. 98. // 串行化对象 99. 对象串 行化，必须实现Serializable接口 100. // 保存 数据到磁盘 101. ObjectOutputStream os = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream(FILENAME))); 102. os.writeObject(serialObject); 103. os.close(); 104. // 读出数据 105. ObjectInputStream is = new ObjectInputStream(new FileInputStream(FILENAME)); 106. is.readObject(); 107. is.close();
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