private void decrypt(File fileIn,String sKey){ 
try{ 
if(sKey.length() == 48){ 
String strPath = fileIn.getPath(); 
if(strPath.substring(strPath.length()-5).toLowerCase().equals(".tdes")) 
strPath = strPath.substring(0,strPath.length()-5); 
else{ 
JOptionPane.showMessageDialog(this,"不是合法的加密文件！",
"提示",JOptionPane.OK_OPTION); 
return; 
} 
JFileChooser chooser = new JFileChooser(); 
chooser.setCurrentDirectory(new File(".")); 
chooser.setSelectedFile(new File(strPath)); 
//用户指定要保存的文件 
int ret = chooser.showSaveDialog(this); 
if(ret==JFileChooser.APPROVE_OPTION){ 
byte[] bytK1 = getKeyByStr(sKey.substring(0,16)); 
byte[] bytK2 = getKeyByStr(sKey.substring(16,32)); 
byte[] bytK3 = getKeyByStr(sKey.substring(32,48)); 
FileInputStream fis = new FileInputStream(fileIn); 
byte[] bytIn = new byte[(int)fileIn.length()]; 
for(int i = 0;i< fileIn.length();i++){ 
bytIn[i] = (byte)fis.read(); 
} 
//解密 
byte[] bytOut = decryptByDES(decryptByDES(decryptByDES(bytIn,bytK3),bytK2),bytK1); 
File fileOut = chooser.getSelectedFile(); 
fileOut.createNewFile(); 
FileOutputStream fos = new FileOutputStream(fileOut); 
for(int i = 0;i< bytOut.length;i++){ 
fos.write((int)bytOut[i]); 
} 
fos.close(); 
JOptionPane.showMessageDialog(this,"解密成功！","提示",JOptionPane.OK_OPTION); 
} 
}else 
JOptionPane.showMessageDialog(this,"密码长度必须等于48！",
"错误信息",JOptionPane.ERROR_MESSAGE); 
}catch(Exception e){ 
JOptionPane.showMessageDialog(this,"解密失败，请核对密码！",
"提示",JOptionPane.OK_OPTION); 
} 
} 

private byte[] encryptByDES(byte[] bytP,byte[] bytKey) throws Exception{ 
DESKeySpec desKS = new DESKeySpec(bytKey); 
SecretKeyFactory skf = SecretKeyFactory.getInstance("DES"); 
SecretKey sk = skf.generateSecret(desKS); 
Cipher cip = Cipher.getInstance("DES"); 
cip.init(Cipher.ENCRYPT_MODE,sk); 
return cip.doFinal(bytP); 
} 

private byte[] decryptByDES(byte[] bytE,byte[] bytKey) throws Exception{ 
DESKeySpec desKS = new DESKeySpec(bytKey); 
SecretKeyFactory skf = SecretKeyFactory.getInstance("DES"); 
SecretKey sk = skf.generateSecret(desKS); 
Cipher cip = Cipher.getInstance("DES"); 
cip.init(Cipher.DECRYPT_MODE,sk); 
return cip.doFinal(bytE); 
}