java文件转化.txt

jxl和JFreeChart 的api初用者可以参照

// 整数到字节数组转换 
 public static byte[] int2bytes(int n) { 
  byte[] ab = new byte[4]; 
  ab[0] = (byte) (0xff & n); 
  ab[1] = (byte) ((0xff00 & n) >> 8); 
  ab[2] = (byte) ((0xff0000 & n) >> 16); 
  ab[3] = (byte) ((0xff000000 & n) >> 24); 
  return ab; 
 } 

 // 字节数组到整数的转换 
 public static int bytes2int(byte b[]) { 
  int s = 0; 
  s = ((((b[0] & 0xff) << 8 | (b[1] & 0xff)) << 8) | (b[2] & 0xff)) << 8 
    | (b[3] & 0xff); 
  return s; 
 } 

 // 字节转换到字符 
 public static char byte2char(byte b) { 
  return (char) b; 
 } 

 private final static byte[] hex = "0123456789ABCDEF".getBytes(); 

 private static int parse(char c) { 
  if (c >= 'a') 
   return (c - 'a' + 10) & 0x0f; 
  if (c >= 'A') 
   return (c - 'A' + 10) & 0x0f; 
  return (c - '0') & 0x0f; 
 } 

 // 从字节数组到十六进制字符串转换 
 public static String Bytes2HexString(byte[] b) { 
  byte[] buff = new byte[2 * b.length]; 
  for (int i = 0; i < b.length; i++) { 
   buff[2 * i] = hex[(b[i] >> 4) & 0x0f]; 
   buff[2 * i + 1] = hex[b[i] & 0x0f]; 
  } 
  return new String(buff); 
 } 

 // 从十六进制字符串到字节数组转换 
 public static byte[] HexString2Bytes(String hexstr) { 
  byte[] b = new byte[hexstr.length() / 2]; 
  int j = 0; 
  for (int i = 0; i < b.length; i++) { 
   char c0 = hexstr.charAt(j++); 
   char c1 = hexstr.charAt(j++); 
   b[i] = (byte) ((parse(c0) << 4) | parse(c1)); 
  } 
  return b; 
 }  

把文件生成byte 字节数组

  FileInputStream   fileForInput   =   new   FileInputStream("d:/test.jpg");   
  String   content   =   new   String();   
  byte[]   bytes=new   byte[fileForInput.available()]; fileForInput.read(bytes); content=new   sun.misc.BASE64Encoder().encode(bytes);   //具体的编码方法   
  fileForInput.close();  

把字节数组转成文件

package com.lizhe;
import java.io.*;
import java.sql.*;
class GetImg {
 
 private File file = null;

 public void blobRead(String outfile, int picID) throws Exception {
  FileOutputStream fos = null;
  InputStream is = null;
  byte[] Buffer = new byte[4096];
  try {
   Class.forName("org.gjt.mm.mysql.Driver").newInstance();
   conn = DriverManager.getConnection(URL);
   pstmt = conn.prepareStatement("select img from imgt where id=?");
   pstmt.setInt(1, picID); // 传入要取的图片的ID
   rs = pstmt.executeQuery();
   rs.next();
   file = new File(outfile);
   if (!file.exists()) {
    file.createNewFile(); // 如果文件不存在，则创建
   }
   fos = new FileOutputStream(file);
   is = rs.getBinaryStream("img");
   int size = 0;
  
   while ((size = is.read(Buffer)) != -1) {
    // System.out.println(size);
    fos.write(Buffer, 0, size);
   }
  } catch (Exception e) {
   System.out.println( e.getMessage());
  } finally {
   // 关闭用到的资源
   fos.close();
   rs.close();
   pstmt.close();
   conn.close();
  }
 }



 

GRANT SELECT,INSERT,UPDATE,DELETE,FILE ON goodemail.* TO wj@% identified by ''