java根据⽂件流判断⽂件类型（后缀名）import java.io.FileInputStream;
public class FileType{
public static String bytesToHexString(byte[] src) {
StringBuilder stringBuilder = new StringBuilder();
if (src == null || src.length <= 0) {
return null;
}
for (int i = 0; i < src.length; i++) {
int v = src[i] & 0xFF;
String hv = HexString(v);
if (hv.length() < 2) {
stringBuilder.append(0);
}
stringBuilder.append(hv);
}
String();
}
/**
* @param args
*/
public static void main(String[] args) throws Exception {
FileInputStream is = new FileInputStream("F:\\相册\\图⽚\\03.jpg");
byte[] b = new byte[3];
String xxx = bytesToHexString(b);
xxx = UpperCase();
System.out.println("头⽂件是：" + xxx);
String ooo = TypeDict.checkType(xxx);
System.out.println("后缀名是：" + ooo);
}
}
public class TypeDict {
/**
常⽤⽂件的⽂件头如下：(以前六位为准)
JPEG (jpg)，⽂件头：FFD8FF
PNG (png)，⽂件头：89504E47
GIF (gif)，⽂件头：47494638
TIFF (tif)，⽂件头：49492A00
Windows Bitmap (bmp)，⽂件头：424D
CAD (dwg)，⽂件头：41433130
Adobe Photoshop (psd)，⽂件头：38425053
Rich Text Format (rtf)，⽂件头：7B5C727466
XML (xml)，⽂件头：3C3F786D6C
HTML (html)，⽂件头：68746D6C3E
Email [thorough only] (eml)，⽂件头：44656C69766572792D646174653A
Outlook Express (dbx)，⽂件头：CFAD12FEC5FD746F
Outlook (pst)，⽂件头：2142444E
MS Word/Excel (doc)，⽂件头：D0CF11E0
MS Access (mdb)，⽂件头：5374616E64617264204A
WordPerfect (wpd)，⽂件头：FF575043
Postscript (ps)，⽂件头：252150532D41646F6265
Adobe Acrobat (pdf)，⽂件头：255044462D312E
Quicken (qdf)，⽂件头：AC9EBD8F
Windows Password (pwl)，⽂件头：E3828596
ZIP Archive (zip)，⽂件头：504B0304
RAR Archive (rar)，⽂件头：52617221
Wave (wav)，⽂件头：57415645
AVI (avi)，⽂件头：41564920
Real Audio (ram)，⽂件头：2E7261FD
system的头文件
Real Media (rm)，⽂件头：2E524D46
MPEG (mpg)，⽂件头：000001BA
MPEG (mpg)，⽂件头：000001B3
Quicktime (mov)，⽂件头：6D6F6F76
Windows Media (asf)，⽂件头：3026B2758E66CF11
MIDI (mid)，⽂件头：4D546864
*/
public static String checkType(String xxxx) {
switch (xxxx) {
case "FFD8FF": return "jpg";
case "89504E": return "png";
case "474946": return "jif";
default: return "0000";
}    } }