問題描述

public static void main(String[] args) throws Exception {File sourceFile = new File('/home/joy/圖片/img1-lg.jpg');File tempFile = new File('/home/joy/桌面/TempFile');saveTempFile(sourceFile, tempFile);String str = byteToString(tempFile);File saveFile = new File('/home/joy/桌面/saveFile.jpg');StringTobyte(str,saveFile); } // 保存臨時文件 public static void saveTempFile(File sourceFile, File tempFile) throws Exception {FileInputStream inputStream = new FileInputStream(sourceFile);FileOutputStream fileOutputStream = new FileOutputStream(tempFile);byte[] buf = new byte[10 * 1024];int readLeng = 0;while ((readLeng = inputStream.read(buf)) != -1) { fileOutputStream.write(buf, 0, readLeng); fileOutputStream.flush();}fileOutputStream.close();inputStream.close(); } // 文件字節轉字符串 public static String byteToString(File file) throws Exception {StringBuilder returnDatas = new StringBuilder();FileInputStream fileInputStream = new FileInputStream(file);byte[] buf = new byte[10 * 1024];int readLenth = 0;while ((readLenth = fileInputStream.read(buf)) != -1) { returnDatas.append(new String(buf,0,readLenth));}fileInputStream.close();return returnDatas.toString(); } // 字符串轉文件 public static void StringTobyte(String str,File file) throws Exception {FileOutputStream fileOutputStream = new FileOutputStream(file);fileOutputStream.write(str.getBytes());fileOutputStream.close(); }

代碼大意：把一張圖片通過字節流轉成一個字符串，然后在獲取該字符串的字節后還原為文件。理解中，字符只是多帶一層編碼，還原成字節后應該還是能獲取到源文件的呀。

問題解答

while ((readLenth = fileInputStream.read(buf)) != -1) { returnDatas.append(new String(buf,0,readLenth));}

二進制圖片文件read出來的不是合法的字符串，其中無法解析的二進制數據會被濾掉參考 javadoc 中的描述：

This method always replaces malformed-input and unmappable-character sequences with this charset’s default replacement string.

編碼和解碼不一定是無損的。你從一個圖片文件讀出一個能無損編解碼的字節流的可能性非常小。

new String( new byte[] { 0xff } ).getBytes()=> [-17, -65, -67]回答3：

首先保證序列化，你可以用base64，才能保證轉回來沒問題