参考博客http://blog.csdn.net/shixing_11/article/details/5708145

每个文件类型都对应着一个编码头部

下面这些是已知的文件头部[自定义的枚举类型]

package org.masque.file;
/*** * Description:文件对应的文件头,资源来自网络* FileHead.java Create on 2014年6月22日 下午1:14:03 * @author masque.java@outlook.com* @version 1.0* Copyright (c) 2014 Company,Inc. All Rights Reserved.*/
public enum FileHead {JPG("jpg", "FFD8FF"), //JPEG (jpg)  PNG("png", "89504E47"),  //PNG (png)  GIF("gif", "47494638"),  //GIF (gif)  TIF("tif", "49492A00"),  //TIFF (tif)  BMP("bmp", "424D"), //Windows Bitmap (bmp)  DWG("dwg", "41433130"), //CAD (dwg)  HTML("html", "68746D6C3E"),  //HTML (html)  RTF("rtf", "7B5C727466"),  //Rich Text Format (rtf)  XML("xml", "3C3F786D6C"),  ZIP("zip", "504B0304"),  RAR("rar", "52617221"),  PSD("psd", "38425053"),  //Photoshop (psd)  EML("eml", "44656C69766572792D646174653A"),  //Email [thorough only] (eml)  DBX("dbx", "CFAD12FEC5FD746F"),  //Outlook Express (dbx)  PST("pst", "2142444E"),  //Outlook (pst)  DOC_XLS("doc_xls", "D0CF11E0"),  //MS Excel 注意：word 和 excel的文件头一样  MDB("mdb", "5374616E64617264204A"),  //MS Access (mdb)  WPD("wpd", "FF575043"), //WordPerfect (wpd)   EPS("eps", "252150532D41646F6265"),  PS("ps", "252150532D41646F6265"),  PDF("pdf", "255044462D312E"),  //Adobe Acrobat (pdf)  QDF("qdf", "AC9EBD8F"),  //Quicken (qdf)  PWL("pwl", "E3828596"),  //Windows Password (pwl)  WAV("wav", "57415645"),  //Wave (wav)  AVI("avi", "41564920"),  RAM("ram", "2E7261FD"),  //Real Audio (ram)  RM("rm", "2E524D46"), //Real Media (rm)  MPG("mpg", "000001BA"),  //  MOV("mov", "6D6F6F76"),  //Quicktime (mov)  ASF("asf", "3026B2758E66CF11"), //Windows Media (asf)  MID("mid", "4D546864");  //MIDI (mid)  private String type;private String code;FileHead(String type,String code){this.type = type;this.code = code;}public String getType() {return type;}public String getCode() {return code;}public static FileHead getLikeCode(String code){System.out.println(code);if (code==null||"".equals(code)) return null;code = code.toUpperCase();FileHead [] fhs = FileHead.values();for (FileHead fh:fhs) {//模糊匹配文件头if (code.startsWith(fh.code)) {return fh;}}return null;}public static FileHead getByType(String type){FileHead [] fhs = FileHead.values();for (FileHead fh:fhs) {if (fh.getType().equals(type)) {return fh;}}return null;}public static FileHead getByCode(String code){FileHead [] fhs = FileHead.values();for (FileHead fh:fhs) {if (fh.getCode().equals(code)) {return fh;}}return null;}
}

 使用方法如下

package org.masque.file;import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
/*** * Description: 读取文件的前部分字节在已知的库中比对* CheckFileHead.java Create on 2014年6月22日 下午1:48:09 * @author masque.java@outlook.com* @version 1.0* Copyright (c) 2014 Company,Inc. All Rights Reserved.*/
public class CheckFileHead {public static void main(String[] args) {String fileHeadStr = getFileByFile(new File("C:/40882199905262314.jpg"));FileHead fileHead = FileHead.getLikeCode(fileHeadStr);System.out.println(fileHead!=null?fileHead.getType():"未知的文件类型!");}public final static String getFileByFile(File file)    {    String filetype = null;    byte[] b = new byte[30];    try    {    InputStream is = new FileInputStream(file);    is.read(b);    filetype = getFileHexString(b);is.close();    }    catch (FileNotFoundException e)    {    e.printStackTrace();    }    catch (IOException e)    {    e.printStackTrace();    }    return filetype;    }    public final static String getFileHexString(byte[] b)    {    StringBuilder stringBuilder = new StringBuilder();    if (b == null || b.length <= 0)    {    return null;    }    for (int i = 0; i < b.length; i++)    {    int v = b[i] & 0xFF;    String hv = Integer.toHexString(v);    if (hv.length() < 2)    {    stringBuilder.append(0);    }    stringBuilder.append(hv);    }    return stringBuilder.toString();    }    
}

 代码比较简单就不做详细介绍