Java String from InputStream [duplicate]

Question

This question already has answers here:

Closed 15 years ago.

Possible Duplicates:
How do I convert an InputStream to a String in Java?
In Java how do a read an input stream in to a string?

I have an InputSteam and need to simply get a single simple String with the complete contents.

How is this done in Java?

• Thomas Owens: Can you elaborate? By definition, a Stream is unbounded. Unless there are some more constraints, you can't get a String (something of fixed size) from an unbounded stream.
• bakkal: This has been asked many times: stackoverflow.com/questions/1763789/…
• Patrick Kafka: stackoverflow.com/questions/309424/…
• x4u: How to do it with nio FileChannel: stackoverflow.com/questions/326390
• Richard Le Mesurier: Awesome solution here: Read/convert an InputStream to a String

Answer 1

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();
}

• tc.: +1 more sane encoding handling.

Answer 2

You need to construct an InputStreamReader to wrap the input stream, converting between binary data and text. Specify the appropriate encoding based on your input source.

Once you've got an InputStreamReader, you could create a BufferedReader and read the contents line by line, or just read buffer-by-buffer and append to a StringBuilder until the read() call returns -1.

The Guava library makes the second part of this easy - use CharStreams.toString(inputStreamReader).

• Thomas Owens: I've never tried this, but shouldn't you be aware of what the stream represents before you do this? If you were to have a stream such that read() would never return -1, there would be no value in even trying this. But, at the same time, I can't think of a stream off the top of my head that never ends.
• Jon Skeet: @Thomas: Well, you could easily create a stream which only ever gave random numbers. I was assuming that the question was asked in a situation where the concept of "read to the end of the stream" did actually make sense...

Answer 3

Here is an example code adapted from here.

public String convertStreamToString(InputStream is) throws IOException {
 /*
 * To convert the InputStream to String we use the BufferedReader.readLine()
 * method. We iterate until the BufferedReader return null which means
 * there's no more data to read. Each line will appended to a StringBuilder
 * and returned as String.
 */
 if (is != null) {
 StringBuilder sb = new StringBuilder();
 String line;
 try {
 BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));
 while ((line = reader.readLine()) != null) {
 sb.append(line).append("\n");
 }
 } finally {
 is.close();
 }
 return sb.toString();
 } else { 
 return "";
 }
 }

• Jon Skeet: Note that that will normalize line endings - it won't necessarily return the exact original text data.
• Gopi: true. edited code to incorporate your suggestion.
• Justin Ardini: Now it won't include the line endings at all. I think Jon Skeet was just saying that every line ending \r\n (or \r) becomes \n.
• Gopi: aaah. thanks for bringing it to notice. reverted.

Answer 4

You can also use Apache Commons IO library

Specifically, you can use IOUtils#toString(InputStream inputStream) method

• Thomas Owens: As a software engineer, I love this. Reusing existing libraries to get the job done. Apache Commons (and all of the Apache projects in general) are very well done and quite helpful in a number of situations.
• siegi: Note that using the method above uses the platforms default encoding, i.e. the result depends on user settings or other external factors. Most of the time it is better to use a method expecting the encoding as additional parameter. See this comment on a related question. Apaches IOUtils provides such methods, too. BTW, the link to Javadoc is broken...

Answer 5

You could also use a StringWriter as follows; each read from your InputStream is matched with a write (or append) to the StringWriter, and upon completion you can call getBuffer to get a StringBuffer which could be used directly or you could get call its toString method.

Answer 6

Wrap the Stream in a Reader to get locale conversion, and then keep reading while collecting in a StringBuffer. When done, do a toString() on the StringBuffer.