如何在將字節數組轉換爲字符串後將新的行字符寫入Java文件

Question

我想讀取文本文件，將其轉換爲字節數組，然後將其寫入另一個文件。爲此，我不想丟失任何換行符，以便新行也應寫入上一步創建的新文件中。這是我迄今所做的：

StringBuilder line=null; 
      try (BufferedReader in = new BufferedReader(new FileReader(filePath))) { 
       line = new StringBuilder(); 
       String tempLine=null; 
       fileSelect=true; 
       while ((tempLine=in.readLine()) != null) {      
        line.append(tempLine+System.lineSeparator()); 
       } 
      } 

      byte[] plaintext =String.valueOf(line).getBytes("UTF-8"); 

    // Encrypt the data 
      byte[] encrypted = cipher.doFinal(plaintext); 
      //String enc=new String(encrypted); 

      try (FileOutputStream out = new FileOutputStream(fileName)) { 
       out.write(encrypted); 
      } 

採取文件路徑和文件名作爲有效的標識符在上面的代碼片斷。

Answer 1

將加密行直接寫入字節並將CRLF用作分隔符是沒有意義的，因爲CRLF是加密數據的合法字節序列。

你還需要兼容格式的每一個加密線路，如Base64編碼：

public static void main(String[] args) throws IOException 
{ 
    File source = new File("path/to/source/file"); 
    File target = new File("path/to/target/file"); 

    List<String> lines = FileUtils.readLines(source, "UTF-8"); 

    for(String line : lines) 
    { 
     byte[] encrypted = someEncryptionMethod(line.getBytes("UTF-8")); 

     String base64 = Base64.encodeBase64String(encrypted); 

     FileUtils.write(target, base64 + "\r\n", true); 
    } 

} 

UPDATE

僅根據你的要求，這是你應該期待什麼：

File source = new File("path/to/source/file"); 
File target = new File("path/to/target/file"); 

byte[] bytes = FileUtils.readFileToByteArray(source); 

byte[] bytes2 = process(bytes); 

FileUtils.writeByteArrayToFile(target, bytes2); 

Answer 2

我不明白你爲什麼要將使用StringBuilder組成的字符串轉換爲字節數組，但是n evertheless，試試這個代碼：

String text = "hallo!\n" + "How do\n" + "you do?\n"; 
System.out.println("Before conversion:"); 
System.out.print(text); 
ByteArrayInputStream is = new ByteArrayInputStream(text.getBytes(Charset.forName("UTF-8"))); 
StringBuilder builder = new StringBuilder(); 
try (BufferedReader in = new BufferedReader(new InputStreamReader(is))) { 
    String line; 
    while ((line = in.readLine()) != null) builder.append(line + lineSeparator()); 
} 
byte[] bytes = builder.toString().getBytes(Charset.forName("UTF-8")); 
System.out.println("After conversion:"); 
System.out.print(new String(bytes, "UTF-8")); 

OUTPUT：

Before conversion: 
hallo! 
How do 
you do? 

After conversion: 
hallo! 
How do 
you do?