Convert Contents Of A ByteArrayInputStream To String

Question

I read this post but I am not following. I have seen this but have not seen a proper example of converting a ByteArrayInputStream to String using a ByteArrayOutputStream.

To retrieve the contents of a ByteArrayInputStream as a String, is using a ByteArrayOutputstream recommended or is there a more preferable way?

I was considering this example and extend ByteArrayInputStream and utilize a Decorator to increase functionality at run time. Any interest in this being a better solution to employing a ByteArrayOutputStream?

Eumenides

You probably want an InputStreamReader, as described in the second link that you gave. A ByteArrayOutputStream won't convert the bytes to characters. – Zondra

Do you really have a ByteArrayInputStream (which implies you have a byte[]) or do you just have an InputStream? – Bunch

@BrettOkken I really have a ByteArrayInputStream whose constructor is passed an array of bytes (varying size) – Eumenides

@DavidWallace There was a reply to the post in the second link using an InputstreamReader: The problem with this is that it reads only up to and including the first line separator. It assumes that the string you're looking for does not contain any line separators. Often that's true, but if not, this won't really work. Why I am not proceeding with that example. – Eumenides

But you can just keep reading from it until it's empty. – Zondra

Answer 1

A ByteArrayOutputStream can read from any InputStream and at the end yield a byte[].

However with a ByteArrayInputStream it is simpler:

int n = in.available();
byte[] bytes = new byte[n];
in.read(bytes, 0, n);
String s = new String(bytes, StandardCharsets.UTF_8); // Or any encoding.

For a ByteArrayInputStream available() yields the total number of bytes.

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Addendum 2021-11-16

Since java 9 you can use the shorter readAllBytes.

byte[] bytes = in.readAllBytes();

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Answer to comment: using ByteArrayOutputStream

ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buf = new byte[8192];
for (;;) {
    int nread = in.read(buf, 0, buf.length);
    if (nread <= 0) {
        break;
    }
    baos.write(buf, 0, nread);
}
in.close();
baos.close();
byte[] bytes = baos.toByteArray();

Here in may be any InputStream.

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Since java 10 there also is a ByteArrayOutputStream#toString(Charset).

String s = baos.toString(StandardCharsets.UTF_8);

Glaucoma

How would a ByteArrayOutputStream read from a ByteArrayInputStream? – Eumenides

I have extended the answer. In principle one loops reading from the InputStream and writing to the ByteArrayOutputStream. Out of tradition the I/O buffer has a ritual size being a power of 2. – Glaucoma

Agree with power of 2 size; I like that and thank you. – Eumenides

From the javadoc of the InputStream.available() function: It is never correct to use the return value of this method to allocate a buffer intended to hold all data in this stream. – Gretchen

@Gretchen true, I did not state that in is that ByteArrayInputStream. For ByteArrayInputStream#available() one may. – Glaucoma

Answer 2

Why nobody mentioned org.apache.commons.io.IOUtils?

import java.nio.charset.StandardCharsets;
import org.apache.commons.io.IOUtils;

String result = IOUtils.toString(in, StandardCharsets.UTF_8);

Just one line of code.

Counterstatement

I added the two required import statements so that not everyone has to search for them. Sorry... it's not just one line of code anymore ;) – Diversified

Sorry but I think this answer is not correct. Because if your input is ByteArrayInputStream you will get compile error. The correct input for this function is InputStream – Seaver

Answer 3

Java 9+ solution:

new String(inputStream.readAllBytes(), StandardCharsets.UTF_8);

Hiccup

Answer 4

Use Scanner and pass to it's constructor the ByteArrayInputStream then read the data from your Scanner , check this example :

ByteArrayInputStream arrayInputStream = new ByteArrayInputStream(new byte[] { 65, 80 });
Scanner scanner = new Scanner(arrayInputStream);
scanner.useDelimiter("\\Z");//To read all scanner content in one String
String data = "";
if (scanner.hasNext())
    data = scanner.next();
System.out.println(data);

Ponderous

If I have XML or HTML doc, will I be able read it without limitations? – Eumenides

Yes, there is no limitation . – Ponderous

Answer 5

Use Base64 encoding

Assuming you got your ByteArrayOutputStream :

ByteArrayOutputStream baos =...
String s = new String(Base64.Encoder.encode(baos.toByteArray()));

See http://docs.oracle.com/javase/8/docs/api/java/util/Base64.Encoder.html

Remembrance

Nice solution. But, I would need to first connect my ByteArrayInputStream into my ByteArrayOutputStream. How is that accomplished? – Eumenides

It's important to say that the Base64.Encoder was released in the Java 8. :) – Diathermy

It should be String s = new String(Base64.getEncoder().encode(baos.toByteArray())); thanks though. – Devisee

As @SiddharthGharge said the encoder creation is wrong. Also question is about InputStream, not OutputStream. – Wundt