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(shuō)明字節(jié)數(shù)組足夠大
????int?j?=?1;???//定義一個(gè)j來(lái)計(jì)數(shù)
????//i?<?bytes???因?yàn)闆](méi)有讀到最后，所以是這樣寫
????for?(int?i?=?0;?i?<?bytes;?i++)?{
????????if?(buf[i]?<=?0xf)?{??//個(gè)位數(shù)補(bǔ)0
????????????System.out.print("0");
????????}
????????System.out.print(Integer.toHexString(buf[i]?&?0xff)+"??");
????????if?(j++?%?10?==?0)?{??//每輸出10個(gè)byte換行
????????????System.out.println();
????????}
????}

輸出結(jié)果所有的都加了0，而不是只有一位數(shù)的才加0，為什么