用过的读写

1、从文件中读取三行数据

 1 String[] lines = new String[3];
 2 boolean readPointerFileSuccess = true;
 3 
 4 try (Scanner scanner = new Scanner(pointerFile)) {
 5     for (int i = 0; i < lines.length; i++) {
 6         if (scanner.hasNextLine()) {
 7             lines[i] = scanner.nextLine();
 8         } else {
 9             readPointerFileSuccess = false;
10         }
11     }
12 }
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 2、写入文件

1 try(PrintWriter writer = new PrintWriter(pointerFile)){
2     writer.println(logFileName);
3     writer.println(pointer);
4     SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
5     String time = sdf.format(readDate);
6     writer.println(time);
7     writer.flush();//立即写入
8 }
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3、RandomAccessFile读取数据

 1 RandomAccessFile randAccessFile = new RandomAccessFile(fileName, "r");
 2 // 定位到文件的 pointer
 3 randAccessFile.seek(pointer);
 4 
 5 String line = readLine(randAccessFile, "GBK");
 6         
 7         
 8 public String readLine(RandomAccessFile randAccessFile, String charset) throws IOException {
 9 
10 ByteArrayOutputStream baos = new ByteArrayOutputStream();
11 
12 int c = -1;
13 boolean eol = false;
14 
15 while (!eol) {
16     switch (c = randAccessFile.read()) {
17     case -1:
18     case '\n':
19         eol = true;
20         break;
21     case '\r':
22         eol = true;
23         long cur = randAccessFile.getFilePointer();
24         if ((randAccessFile.read()) != '\n') {
25             randAccessFile.seek(cur);
26         }
27         break;
28     default:
29         baos.write(c);
30         break;
31     }
32 }
33 
34 if ((c == -1) && (baos.size() == 0)) {
35     return null;
36 }
37 
38 return new String(baos.toByteArray(), charset);
39 }
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4、RandomAccessFile读取数据

 1     File file = new File(info.getName());
 2 
 3     RandomAccessFile raf = null;
 4     try {
 5         raf = new RandomAccessFile(file, "rw");
 6     } catch (FileNotFoundException e) {
 7         e.printStackTrace();
 8     }
 9 
10     FileChannel cha = raf.getChannel();
11 
12     ByteBuffer buf = ByteBuffer.allocate(1024);
13 
14     int size = 0;
15 
16     StringBuffer sb = new StringBuffer();
17 
18     try {
19         while ((size = cha.read(buf)) != -1) {
20 
21             buf.flip();
22 
23             byte[] buff = new byte[size];
24 
25             buf.get(buff);
26 
27             sb.append(new String(buff, 0, size));
28 
29         }
30     } catch (IOException e) {
31         e.printStackTrace();
32     }
33 
34     String[] s = sb.toString().split("\\}\\,\\{");
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posted @ 2016-12-26 17:45  Orc_Warrior  阅读(119)  评论(0)  编辑  收藏  举报