How to Read/Convert an Inputstream into a String in Java

How do I read / convert an InputStream into a String in Java?

A nice way to do this is using Apache commons IOUtils to copy the InputStream into a StringWriter... something like

StringWriter writer = new StringWriter();
IOUtils.copy(inputStream, writer, encoding);
String theString = writer.toString();

or even

// NB: does not close inputStream, you'll have to use try-with-resources for that
String theString = IOUtils.toString(inputStream, encoding); 

Alternatively, you could use ByteArrayOutputStream if you don't want to mix your Streams and Writers

How do I read / convert an InputStream into a String in Java?

A nice way to do this is using Apache commons IOUtils to copy the InputStream into a StringWriter... something like

StringWriter writer = new StringWriter();
IOUtils.copy(inputStream, writer, encoding);
String theString = writer.toString();

or even

// NB: does not close inputStream, you'll have to use try-with-resources for that
String theString = IOUtils.toString(inputStream, encoding); 

Alternatively, you could use ByteArrayOutputStream if you don't want to mix your Streams and Writers

How do I convert an InputStream to a String in Java?

This is my version,

public static String readString(InputStream inputStream) throws IOException {

    ByteArrayOutputStream into = new ByteArrayOutputStream();
    byte[] buf = new byte[4096];
    for (int n; 0 < (n = inputStream.read(buf));) {
        into.write(buf, 0, n);
    }
    into.close();
    return new String(into.toByteArray(), "UTF-8"); // Or whatever encoding
}

Java String from InputStream

Here is a modification of Gopi's answer that doesn't have the line ending problem and is also more effective as it doesn't need temporary String objects for every line and avoids the redundant copying in BufferedReader and the extra work in readLine().

public static String convertStreamToString( InputStream is, String ecoding ) throws IOException
{
    StringBuilder sb = new StringBuilder( Math.max( 16, is.available() ) );
    char[] tmp = new char[ 4096 ];

    try {
       InputStreamReader reader = new InputStreamReader( is, ecoding );
       for( int cnt; ( cnt = reader.read( tmp ) ) > 0; )
            sb.append( tmp, 0, cnt );
    } finally {
        is.close();
    }
    return sb.toString();
}

Convert InputStream into StreamString given a Charset

I think you can try:

Stream<String> lines = new BufferedReader(new InputStreamReader(is, cs)).lines();

Convert Contents Of A ByteArrayInputStream To String

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);

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