[ACCEPTED]-How can I get a java.io.InputStream from a java.lang.String?-inputstream

Accepted answer
Score: 78

Update: This answer is precisely what the OP doesn't 4 want. Please read the other answers.

For 3 those cases when we don't care about the 2 data being re-materialized in memory, please 1 use:

new ByteArrayInputStream(str.getBytes("UTF-8"))
Score: 19

If you don't mind a dependency on the commons-io package, then 1 you could use the IOUtils.toInputStream(String text) method.

Score: 5

There is an adapter from Apache Commons-IO 2 which adapts from Reader to InputStream, which 1 is named ReaderInputStream.

Example code:

public void testReaderInputStream() throws IOException {
    InputStream inputStream = new ReaderInputStream(new StringReader("largeString"), StandardCharsets.UTF_8);
    Assert.assertEquals("largeString", IOUtils.toString(inputStream, StandardCharsets.UTF_8));

Reference: https://stackoverflow.com/a/27909221/5658642

Score: 3

To my mind, the easiest way to do this is 10 by pushing the data through a Writer:

public class StringEmitter {
  public static void main(String[] args) throws IOException {
    class DataHandler extends OutputStream {
      public void write(final int b) throws IOException {
        write(new byte[] { (byte) b });
      public void write(byte[] b) throws IOException {
        write(b, 0, b.length);
      public void write(byte[] b, int off, int len)
          throws IOException {
        System.out.println("bytecount=" + len);

    StringBuilder sample = new StringBuilder();
    while (sample.length() < 100 * 1000) {

    Writer writer = new OutputStreamWriter(
        new DataHandler(), "UTF-16");

The 9 JVM implementation I'm using pushed data 8 through in 8K chunks, but you could have 7 some affect on the buffer size by reducing 6 the number of characters written at one 5 time and calling flush.

An alternative to 4 writing your own CharsetEncoder wrapper 3 to use a Writer to encode the data, though 2 it is something of a pain to do right. This 1 should be a reliable (if inefficient) implementation:

/** Inefficient string stream implementation */
public class StringInputStream extends InputStream {

  /* # of characters to buffer - must be >=2 to handle surrogate pairs */
  private static final int CHAR_CAP = 8;

  private final Queue<Byte> buffer = new LinkedList<Byte>();
  private final Writer encoder;
  private final String data;
  private int index;

  public StringInputStream(String sequence, Charset charset) {
    data = sequence;
    encoder = new OutputStreamWriter(
        new OutputStreamBuffer(), charset);

  private int buffer() throws IOException {
    if (index >= data.length()) {
      return -1;
    int rlen = index + CHAR_CAP;
    if (rlen > data.length()) {
      rlen = data.length();
    for (; index < rlen; index++) {
      char ch = data.charAt(index);
      // ensure data enters buffer
    if (index >= data.length()) {
    return buffer.size();

  public int read() throws IOException {
    if (buffer.size() == 0) {
      int r = buffer();
      if (r == -1) {
        return -1;
    return 0xFF & buffer.remove();

  private class OutputStreamBuffer extends OutputStream {

    public void write(int i) throws IOException {
      byte b = (byte) i;


Score: 2

Well, one possible way is to:

  • Create a PipedOutputStream
  • Pipe it to a PipedInputStream
  • Wrap an OutputStreamWriter around the PipedOutputStream (you can specify the encoding in the constructor)
  • Et voil&aacute;, anything you write to the OutputStreamWriter can be read from the PipedInputStream!

Of course, this 2 seems like a rather hackish way to do it, but 1 at least it is a way.

Score: 1

A solution is to roll your own, creating 3 an InputStream implementation that likely would use 2 java.nio.charset.CharsetEncoder to encode each char or chunk of chars to an array 1 of bytes for the InputStream as necessary.

Score: 0

You can take help of org.hsqldb.lib library.

public StringInputStream(String paramString)
    this.str = paramString;
    this.available = (paramString.length() * 2);


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