字节流转成字符串之后，在通过字符串转成字节流后的文件为什么会不一样？

Question

public static void main(String[] args) throws Exception { File sourceFile = new File("/home/joy/图片/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); } // 保存临时文件 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(); } // 文件字节转字符串 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(); } // 字符串转文件 public static void StringTobyte(String str,File file) throws Exception { FileOutputStream fileOutputStream = new FileOutputStream(file); fileOutputStream.write(str.getBytes()); fileOutputStream.close(); } 代码大意：把一张图片通过字节流转成一个字符串，然后在获取该字符串的字节后还原为文件。理解中，字符只是多带一层编码，还原成字节后应该还是能获取到源文件的呀。

Answer 1

编码和解码不一定是无损的。你从一个图片文件读出一个能无损编解码的字节流的可能性非常小。

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

Answer 2

首先保证序列化，你可以用base64，才能保证转回来没问题