java如何把二进制内容(字符串)保存成文件

Question

二进制内容由xml中提交过来的，需要把它转成文件保存到指定目录中。
二进制内容:FFD8FFE000104A46494600010100000100010000FFDB0043000503040404030504040405050506070C08070707070F.....

Answer 1

先将其hex解码然后写输出流
[code="java"]
/*

• @(#)TestHex.java *
• Summary: Demonstrate how to handle hex strings. *
• Copyright: (c) 2009-2010 Roedy Green, Canadian Mind Products, http://mindprod.com *
• Licence: This software may be copied and used freely for any purpose but military.
• http://mindprod.com/contact/nonmil.html *
• Requires: JDK 1.6+ *
• Created with: IntelliJ IDEA IDE. *
• Version History:
• 1.0 2009-06-05 - initial version. */ package com.mindprod.example;

import static java.lang.System.out;

/**

• Demonstrate how to handle hex strings. *
• @author Roedy Green, Canadian Mind Products
• @version 1.0 2009-06-05 - initial version.

• @since 2009-06-05
  /
  public final class TestHex
  {
  /*

  • precomputed translate table for chars 0..'f' */ private static byte[] correspondingNibble = new byte['f' + 1]; // -------------------------- PUBLIC STATIC METHODS --------------------------

  /**

  • Convert a hex string to an unsigned byte array.
  • Permits upper or lower case hex. *
  • @param s String must have even number of characters.
  • and be formed only of digits 0-9 A-F or
  • a-f. No spaces, minus or plus signs. *

  • @return corresponding unsigned byte array. see http://mindprod.com/jgloss/unsigned.html
    */
    public static byte[] fromHexString( String s )
    {
    int stringLength = s.length();
    if ( ( stringLength & 0x1 ) != 0 )
    {
    throw new IllegalArgumentException( "fromHexString requires an even number of hex characters" );
    }
    byte[] bytes = new byte[stringLength / 2];

    for ( int i = 0, j = 0; i < stringLength; i += 2, j++ )
    {
    int high = charToNibble( s.charAt( i ) );
    int low = charToNibble( s.charAt( i + 1 ) );
    // You can store either unsigned 0..255 or signed -128..127 bytes in a byte type.
    bytes[ j ] = ( byte ) ( ( high << 4 ) | low );
    }
    return bytes;
    }

// -------------------------- STATIC METHODS --------------------------

static
    {
    // only 0..9 A..F a..f have meaning. rest are errors.
    for ( int i = 0; i <= 'f'; i++ )
        {
        correspondingNibble[ i ] = -1;
        }
    for ( int i = '0'; i <= '9'; i++ )
        {
        correspondingNibble[ i ] = ( byte ) ( i - '0' );
        }
    for ( int i = 'A'; i <= 'F'; i++ )
        {
        correspondingNibble[ i ] = ( byte ) ( i - 'A' + 10 );
        }
    for ( int i = 'a'; i <= 'f'; i++ )
        {
        correspondingNibble[ i ] = ( byte ) ( i - 'a' + 10 );
        }
    }

/**
 * convert  a single char to corresponding nibble using a precalculated array.
 * Based on code by:
 * Brian Marquis
 * Orion Group Software Engineers http://www.ogse.com
 *
 * @param c char to convert. must be 0-9 a-f A-F, no
 *          spaces, plus or minus signs.
 *
 * @return corresponding integer  0..15
 * @throws IllegalArgumentException on invalid c.
 */
private static int charToNibble( char c )
    {
    if ( c > 'f' )
        {
        throw new IllegalArgumentException( "Invalid hex character: " + c );
        }
    int nibble = correspondingNibble[ c ];
    if ( nibble < 0 )
        {
        throw new IllegalArgumentException( "Invalid hex character: " + c );
        }
    return nibble;
    }

/**
 * code not used, for explanation only.
 * convert a single char to corresponding nibble.
 * Slow version, easier to understand.
 *
 * @param c char to convert. must be 0-9 a-f A-F, no
 *          spaces, plus or minus signs.
 *
 * @return corresponding integer
 */
private static int slowCharToNibble( char c )
    {
    if ( '0' <= c && c <= '9' )
        {
        return c - '0';
        }
    else if ( 'a' <= c && c <= 'f' )
        {
        return c - 'a' + 0xa;
        }
    else if ( 'A' <= c && c <= 'F' )
            {
            return c - 'A' + 0xa;
            }
        else
            {
            throw new IllegalArgumentException( "Invalid hex character: " + c );
            }
    }

// --------------------------- main() method ---------------------------

/**
 * Test harness
 *
 * @param args not used
 */
public static void main( String[] args )
    {
    String hexString = "FFD8FFE000104A46494600010100000100010000FFDB0043000503040404030504040405050506070C08070707070F";
    out.println( hexString );
    // convert hex string to an array of bytes
    byte[] bytes = fromHexString( hexString );
    out.println( bytes.length + " bytes long" );

try{
OutputStream os=new FileOutputStream("d:\a.data");
os.write(bytes);
os.flush();
os.close();
}catch(Exception ex){
ex.printStackTrace();
}
}
}
[/code]