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

Question

Given a string:

String exampleString = "example";

How do I convert it to an InputStream?

• Thorbjørn Ravn Andersen: InputStreams look at bytes, Readers look at characters.

Answer 1

Like this:

InputStream stream = new ByteArrayInputStream(exampleString.getBytes(StandardCharsets.UTF_8));

Note that this assumes that you want an InputStream that is a stream of bytes that represent your original string encoded as UTF-8.

For versions of Java less than 7, replace StandardCharsets.UTF_8 with "UTF-8".

• Jonathan Ramos: Doesn't this charset get lost when doing: String --> bytes --> ByteArrayInputStream ? When trying this on a for example "ü", the bytes will have the right letter, but the ByteArrayInputStream will have lost the right conversion. Or am I wrong?
• Nantoka: StandardCharsets requires minimum API level 19.
• Cruncher: @JonathanRamos it's not up to the stream to hold the conversion. It's up to whatever is decoding the bytes back into strings.
• PJ_Finnegan: @Nantoka Instead of StandardCharsets.UTF_8 you can use Charset.forName("UTF-8") for any API Level.
• Dave Moten: Not pretty if you have large string objects and want to save on memory/allocations. A proper streaming solution would be nice.

Answer 2

I find that using Apache Commons IO makes my life much easier.

String source = "This is the source of my input stream";
InputStream in = org.apache.commons.io.IOUtils.toInputStream(source, "UTF-8");

You may find that the library also offer many other shortcuts to commonly done tasks that you may be able to use in your project.

• Pankaj Kumar: They used new ByteArrayInputStream(exampleString.getBytes("UTF-8")). So it will be optimized way to use InputStream stream = new ByteArrayInputStream(exampleString.getBytes("UTF-8"))
• Andrew White: @PankajKumar: Java's JIT compiler is more than able to inline this.
• arkon: Using a method which doesn't specify encoding is a terrible idea...
• Cuga: @b1naryatr0phy: Apache commons includes another form of this method which takes the encoding as a second parameter (which, you're right, is preferable): InputStream in = IOUtils.toInputStream(source, "UTF-8")
• douglaslps: You can use StandardCharsets.UTF_8 definition instead of plain text.

Answer 3

You could use a StringReader and convert the reader to an input stream using the solution in this other stackoverflow post.

Answer 4

There are two ways we can convert String to InputStream in Java,

1. Using ByteArrayInputStream

Example :-

String str = "String contents";
InputStream is = new ByteArrayInputStream(str.getBytes(StandardCharsets.UTF_8));

2. Using Apache Commons IO

Example:-

String str = "String contents"
InputStream is = IOUtils.toInputStream(str, StandardCharsets.UTF_8);

• soMuchToLearnAndShare: Hi @anil do you have opinion /experience which one is better?
• Anil Nivargi: my opinion, using Apache commons IO is better option

Answer 5

You can try cactoos for that.

final InputStream input = new InputStreamOf("example");

The object is created with new and not a static method for a reason.