a little question about DES

my codes is:
-----------------------
 static public void encrypt(String keyStr, File fin, File fout) {
    try {
      SecretKey key = new SecretKeySpec(keyStr.getBytes(), "DES");
      FileInputStream in = new FileInputStream(fin);
      FileOutputStream out = new FileOutputStream(fout);
      Cipher desCipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
      desCipher.init(Cipher.ENCRYPT_MODE, key);
      CipherOutputStream cos = new CipherOutputStream(out, desCipher);
      byte[] enBuffer = new byte[4096];
      int n;
      while ( (n = in.read(enBuffer)) != -1) {
        cos.write(enBuffer, 0, n);
      }
      cos.close();
    }
    catch (Exception e) {
      e.printStackTrace();
    }
  }
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as we know, the DES's key is 56bits

but when I used:
encrypt("1234567", new File("E:/1.txt"), new File("E:/2.txt"));
or
encrypt("123456789", new File("E:/1.txt"), new File("E:/2.txt"));

it throw Exception:
Invalid key length: 7 bytes
or
Invalid key length: 9 bytes

but
encrypt("12345678", new File("E:/1.txt"), new File("E:/2.txt"));
is OK

it means that the key must be 64bits,but DES's key is 56bits,isn't it?
why I used 56bits key it throw Exception?