Read String and bytes from the same file java

Question

I'm looking for a way to switch between reading bytes (as byte[]) and reading lines of Strings from a file. I know that a byte[] can be obtained form a file through a FileInputStream, and a String can be obtained through a BufferedReader, but using both of them at the same time is proving problematic. I know how long the section of bytes are. String encoding can be kept constant from when I write the file. The filetype is a custom one that is still in development, so I can change how I write data to it.

How can I read Strings and byte[]s from the same file in java?

Always read one type and convert when needed? You can convert String to byte[] and byte[] to String. — Simon Arsenault, Jun 18 '13 at 22:17
Why not read the entire file as a byte array and then convert the needed sections to Strings after reading the file in? — AndyPerfect, Jun 18 '13 at 22:18
Use [`DataInputStream`](http://docs.oracle.com/javase/6/docs/api/java/io/DataInputStream.html) and `DataOutputStream` to keep a consistent format? — Louis Wasserman, Jun 18 '13 at 22:31

score 1 · Accepted Answer · edited May 23 '17 at 12:21

Read as bytes. When you have read a sequence of bytes that you know should be a string, place those bytes in an array, put the array inside a ByteArrayInputStream and use that as the underlying InputStream for a Reader to get the bytes as characters, then read those characters to produce a String.

For the later parts of this process see the related SO question on how to create a String from an InputStream.

score 0 · Answer 2 · answered Jun 18 '13 at 22:24

0

Read the file as Strings using a BufferedReader then use String.getBytes().

answered Jun 18 '13 at 22:24

Ravi K Thapliyal

46,997
8
70
84

When you do that, the encoding can mess up some of the original data. – pensono Jun 19 '13 at 01:05

Indu Devanath · Answer 3 · 2013-06-18T23:37:24.163

Why not try this:

        BufferedReader bufferedReader = null;

        try {
            bufferedReader = new BufferedReader(new FileReader("testing.txt"));
            String line = bufferedReader.readLine();
            while(line != null){
                byte[] b = line.getBytes();
            }

        } finally {
            if(bufferedReader!=null){
                bufferedReader.close();
            }
        }

or

            FileInputStream in = null;
        BufferedReader bufferedReader = null;

        try {
            bufferedReader = new BufferedReader(new FileReader("xanadu.txt"));
            String line = bufferedReader.readLine();
            while(line != null){
                //read your line
            }
            in = new FileInputStream("xanadu.txt");
            int c;
            while ((c = in.read()) != -1) {
                //read your bytes (c)
            }


        } finally {
            if (in != null) {
                in.close();
            }
            if(bufferedReader!=null){
                bufferedReader.close();
            }
        }

score 0 · Answer 4 · answered Jun 19 '13 at 17:46

Read everything as bytes from the buffered input stream, and convert string sections into String's using constructor that accepts the byte array:

 String string = new String(bytes, offset, length, "US-ASCII");

Depending on how the data are actually encoded, you may need to use "UTF-8" or something else as the name of the charset.

Read String and bytes from the same file java

4 Answers4