java读取文件(按字符或字节读取)

瓜田守望者 贡献于2012-10-23

作者 韩健  创建于2012-10-23 14:38:00   修改者韩健  修改于2012-10-23 14:38:00字数3651

文档摘要:java读取文件(按字符或字节读取)
关键词:

java读取文件(按字符或字节读取) import java.io.BufferedReader; import java.io.File; import java.io.FileInputStream; import java.io.FileReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.RandomAccessFile; import java.io.Reader; /**  * 读取文件  * @author 张月  * @version 2012-4-25  */ public class ReadFromFile {     /**      * 以字节为单位读取文件,常用于读二进制文件,如图片、声音、影像等文件。      */     public static void readFileByBytes(String fileName) {         File file = new File(fileName);         InputStream in = null;         try {             System.out.println("以字节为单位读取文件内容,一次读一个字节:");             // 一次读一个字节             in = new FileInputStream(file);             int tempbyte;             while ((tempbyte = in.read()) != -1) {                 System.out.write(tempbyte);             }             in.close();         } catch (IOException e) {             e.printStackTrace();             return;         }         try {             System.out.println("以字节为单位读取文件内容,一次读多个字节:");             // 一次读多个字节             byte[] tempbytes = new byte[100];             int byteread = 0;             in = new FileInputStream(fileName);             ReadFromFile.showAvailableBytes(in);             // 读入多个字节到字节数组中,byteread为一次读入的字节数             while ((byteread = in.read(tempbytes)) != -1) {                 System.out.write(tempbytes, 0, byteread);             }         } catch (Exception e1) {             e1.printStackTrace();         } finally {             if (in != null) {                 try {                     in.close();                 } catch (IOException e1) {                 }             }         }     }     /**      * 以字符为单位读取文件,常用于读文本,数字等类型的文件      */     public static void readFileByChars(String fileName) {         File file = new File(fileName);         Reader reader = null;         try {             System.out.println("以字符为单位读取文件内容,一次读一个字节:");             // 一次读一个字符             reader = new InputStreamReader(new FileInputStream(file));             int tempchar;             while ((tempchar = reader.read()) != -1) {                 // 对于windows下,\r\n这两个字符在一起时,表示一个换行。                 // 但如果这两个字符分开显示时,会换两次行。                 // 因此,屏蔽掉\r,或者屏蔽\n。否则,将会多出很多空行。                 if (((char) tempchar) != '\r') {                     System.out.print((char) tempchar);                 }             }             reader.close();         } catch (Exception e) {             e.printStackTrace();         }         try {             System.out.println("以字符为单位读取文件内容,一次读多个字节:");             // 一次读多个字符             char[] tempchars = new char[30];             int charread = 0;             reader = new InputStreamReader(new FileInputStream(fileName));             // 读入多个字符到字符数组中,charread为一次读取字符数             while ((charread = reader.read(tempchars)) != -1) {                  // 同样屏蔽掉\r不显示                 if ((charread == tempchars.length)                         && (tempchars[tempchars.length - 1] != '\r')) {                     System.out.print(tempchars);                 } else {                     for (int i = 0; i < charread; i++) {                         if (tempchars[i] == '\r') {                             continue;                         } else {                             System.out.print(tempchars[i]);                         }                     }                 }             }         } catch (Exception e1) {             e1.printStackTrace();         } finally {             if (reader != null) {                 try {                     reader.close();                 } catch (IOException e1) {                 }             }         }     }     /**      * 以行为单位读取文件,常用于读面向行的格式化文件      */     public static void readFileByLines(String fileName) {         File file = new File(fileName);         BufferedReader reader = null;         try {             System.out.println("以行为单位读取文件内容,一次读一整行:");             reader = new BufferedReader(new FileReader(file));             String tempString = null;             int line = 1;             // 一次读入一行,直到读入null为文件结束             while ((tempString = reader.readLine()) != null) {                 // 显示行号                 System.out.println("line " + line + ": " + tempString);                 line++;             }             reader.close();         } catch (IOException e) {             e.printStackTrace();         } finally {             if (reader != null) {                 try {                     reader.close();                 } catch (IOException e1) {                 }             }         }     }     /**      * 随机读取文件内容      */     public static void readFileByRandomAccess(String fileName) {         RandomAccessFile randomFile = null;         try {             System.out.println("随机读取一段文件内容:");             // 打开一个随机访问文件流,按只读方式             randomFile = new RandomAccessFile(fileName, "r");             // 文件长度,字节数             long fileLength = randomFile.length();             // 读文件的起始位置             int beginIndex = (fileLength > 4) ? 4 : 0;             // 将读文件的开始位置移到beginIndex位置。             randomFile.seek(beginIndex);             byte[] bytes = new byte[10];             int byteread = 0;             // 一次读10个字节,如果文件内容不足10个字节,则读剩下的字节。             // 将一次读取的字节数赋给byteread             while ((byteread = randomFile.read(bytes)) != -1) {                 System.out.write(bytes, 0, byteread);             }         } catch (IOException e) {             e.printStackTrace();         } finally {             if (randomFile != null) {                 try {                     randomFile.close();                 } catch (IOException e1) {                 }             }         }     }     /**      * 显示输入流中还剩的字节数      */     private static void showAvailableBytes(InputStream in) {         try {             System.out.println("当前字节输入流中的字节数为:" + in.available());         } catch (IOException e) {             e.printStackTrace();         }     }     public static void main(String[] args) {         String fileName = "C:/newTemp.txt";         ReadFromFile.readFileByBytes(fileName);         ReadFromFile.readFileByChars(fileName);         ReadFromFile.readFileByLines(fileName);         ReadFromFile.readFileByRandomAccess(fileName);     } }

下载文档到电脑,查找使用更方便

文档的实际排版效果,会与网站的显示效果略有不同!!

需要 3 金币 [ 分享文档获得金币 ] 2 人已下载

下载文档