public?static?void?printHexByByteArray(String?fileName)?throws?IOException{

????FileInputStream?in?=?new?FileInputStream(fileName);

????????byte[]?buf?=?new?byte[20?*?1024];

????int?bytes?=?in.read(buf,0,buf.length);//一次性讀完，說明字節數組足夠大
????int?j?=?1;???//定義一個j來計數
????//i?<?bytes???因為沒有讀到最后，所以是這樣寫
????for?(int?i?=?0;?i?<?bytes;?i++)?{
????????if?(buf[i]?<=?0xf)?{??//個位數補0
????????????System.out.print("0");
????????}
????????System.out.print(Integer.toHexString(buf[i]?&?0xff)+"??");
????????if?(j++?%?10?==?0)?{??//每輸出10個byte換行
????????????System.out.println();
????????}
????}

輸出結果所有的都加了0，而不是只有一位數的才加0，為什么