How to read bytes from a file to a byte[] array?

Question

I am writing a Java program which encrypts a given text using RSA, and saves the encrypted bytes(byte[] array) in a .txt file. There is a separate decryption program which reads these bytes. Now I want to read the same bytes into a byte[] in to the decryption program. How can this be done using Java?

BufferedReader brip = new BufferedReader(new FileReader("encrypted.txt"));
Strings CurrentLine = brip.readLine();
byte[] b = sCurrentLine.getBytes();

This is how I have been reading the data from the file. But it's wrong because it converts the bytes in sCurrentLine variable into again bytes.

Have you tried anything to read it yet? Please demonstrate some attempt at solving your problem by showing example code. If you don't know where to start, Google is always a good bet. — rmlan, Dec 02 '15 at 22:55
Everything is wrong here. Encrypted data is not text; shouldn't be stored in a file named .txt; doesn't contain lines; and can't be read with a `Reader.` Use an `InputStream.` — user207421, Dec 02 '15 at 23:18

score 29 · Answer 1 · edited May 26 '17 at 15:13

29

In Java 7 you can use the readAllBytes() method of Files class. See below:

Path fileLocation = Paths.get("C:\\test_java\\file.txt");
byte[] data = Files.readAllBytes(fileLocation);

There are many other ways to do it see here and here

edited May 26 '17 at 15:13

Der_Meister

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answered Dec 02 '15 at 23:04

Raf

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This only works with smaller files. – laim2003 Mar 05 '21 at 09:07

score 1 · Answer 2 · answered Sep 30 '17 at 10:48

This code worked for me, in an android project so hopefully, it will work for you.

 private byte[] getByte(String path) {
    byte[] getBytes = {};
    try {
        File file = new File(path);
        getBytes = new byte[(int) file.length()];
        InputStream is = new FileInputStream(file);
        is.read(getBytes);
        is.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return getBytes;
}

How to read bytes from a file to a byte[] array?

2 Answers2