[問題] DataInputStream: binary 轉 int(已解決)

看板java作者moers (MOラブリ～)時間10年前 (2015/04/27 19:36)推噓0(0推 0噓 2→)

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各位前輩大大好因為最近要做binary format 轉成一般ascii format而遇到一些問題輸入檔是序列合成資料全都是用binary表示int，其說明： * Binary The file is in the binary format. The items in an itemset are displayed in increasing order, then followed by a -1, which is the itemset delimiter. When all the itemsets in a sequence are output, follows a -2 as the sequence delimiter. Then starts a new sequence. -1當間隔，-2當換行，其他都是數字表示item 然而我卻在轉檔地方卡住，我用DataInputStream的readInt()讀取，以下是我程式碼： DataInputStream br = new DataInputStream(new FileInputStream(args[0])); FileWriter writer = new FileWriter(args[0] + "aspmf"); int intRead; while (br.available() > 0) { intRead = br.readInt(); if (intRead != -2) writer.write(intRead + " "); else writer.write("-2\n"); } 然而輸出黨卻是失敗的： 285212672 385875968 -1 -16777217 50331648 285212672 402653184 -1 33554432 83886080 100663296 134217728 285212672 335544320 369098752 -1 0 1342177 28 167772160 285212672 -1 -16777217 402653184 -1 -16777217 33554432 83886080 100663296 285212672 -1 16777216 33554432 134217728 285212672 3187671 04 369098752 385875968 402653184 -1 33554432 -1 0 83886080 134217728 -1 -16777217 讀的數量沒錯但是轉成int只有-1跟0是轉正確的後來改用byte[]一次讀四個再轉int就沒有問題 // DataInputStream br = new DataInputStream(new FileInputStream(args[0])); FileInputStream br = new FileInputStream(args[0]); FileWriter writer = new FileWriter(args[0] + "aspmf"); byte[] buf = new byte[4]; int intRead; while (br.available() > 0) { br.read(buf); intRead = convertirOctetEnEntier(buf); //intRead = br.readInt(); if (intRead != -2) writer.write(intRead + " "); else writer.write("-2\n"); [B} //這是直接用網路上的，應該是正確的 public static int convertirOctetEnEntier(byte[] b){ int MASK = 0xFF; int result = 0; result = b[0] & MASK; result = result + ((b[1] & MASK) << 8); result = result + ((b[2] & MASK) << 16); result = result + ((b[3] & MASK) << 24); return result; } 輸出結果： 17 23 -1 -2 3 17 24 -1 2 5 6 8 17 20 22 -1 0 8 10 17 -1 -2 24 -1 -2 2 5 6 17 -1 1 2 8 17 19 22 23 24 -1 2 -1 0 5 8 -1 -2 java api說明文件 DataInputStream readInt() Returns: the next four bytes of this input stream, interpreted as an int. 應該是要輸出一樣的東西，還是我對功能有所誤解？附上完整程式碼還有輸入檔 http://git.io/vf9Q6 （點Raw可下載） http://git.io/vf97n 感謝 -- ※ 發信站: 批踢踢實業坊(ptt.cc), 來自: 114.25.178.235 ※ 文章網址: https://www.ptt.cc/bbs/java/M.1430134619.A.617.html ※ 編輯: moers (114.25.178.235), 04/27/2015 19:38:07