How do I read / convert an InputStream into a String in Java
In this tutorial we are going to learn about reading and converting an InputStream into a String in Java.
Summarize other answers I found 11 main ways to do this (see below). And I wrote some performance tests (see results below):
Ways to convert an InputStream to a String:
1.Using IOUtils.toString (Apache Utils)
String result = IOUtils.toString(inputStream, StandardCharsets.UTF_8);2.Using CharStreams (Guava)
String result = CharStreams.toString(new InputStreamReader(
inputStream, Charsets.UTF_8));3.Using Scanner (JDK)
Scanner s = new Scanner(inputStream).useDelimiter("\\A");
String result = s.hasNext() ? s.next() : "";4.Using Stream API (Java 8). Warning: This solution converts different line breaks (like \r\n) to \n.
String result = new BufferedReader(new InputStreamReader(inputStream))
.lines().collect(Collectors.joining("\n"));5.Using parallel Stream API (Java 8). Warning: This solution converts different line breaks (like \r\n) to \n.
String result = new BufferedReader(new InputStreamReader(inputStream))
.lines().parallel().collect(Collectors.joining("\n"));6.Using InputStreamReader and StringBuilder (JDK)
int bufferSize = 1024;
char[] buffer = new char[bufferSize];
StringBuilder out = new StringBuilder();
Reader in = new InputStreamReader(stream, StandardCharsets.UTF_8);
for (int numRead; (numRead = in.read(buffer, 0, buffer.length)) > 0; ) {
out.append(buffer, 0, numRead);
}
return out.toString();7.Using StringWriter and IOUtils.copy (Apache Commons)
StringWriter writer = new StringWriter();
IOUtils.copy(inputStream, writer, "UTF-8");
return writer.toString();8.Using ByteArrayOutputStream and inputStream.read (JDK)
ByteArrayOutputStream result = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
for (int length; (length = inputStream.read(buffer)) != -1; ) {
result.write(buffer, 0, length);
}
// StandardCharsets.UTF_8.name() > JDK 7
return result.toString("UTF-8");9.Using BufferedReader (JDK). Warning: This solution converts different line breaks (like \n\r) to line.separator system property (for example, in Windows to “\r\n”).
String newLine = System.getProperty("line.separator");
BufferedReader reader = new BufferedReader(
new InputStreamReader(inputStream));
StringBuilder result = new StringBuilder();
for (String line; (line = reader.readLine()) != null; ) {
if (result.length() > 0) {
result.append(newLine);
}
result.append(line);
}
return result.toString();10.Using BufferedInputStream and ByteArrayOutputStream (JDK)
BufferedInputStream bis = new BufferedInputStream(inputStream);
ByteArrayOutputStream buf = new ByteArrayOutputStream();
for (int result = bis.read(); result != -1; result = bis.read()) {
buf.write((byte) result);
}
// StandardCharsets.UTF_8.name() > JDK 7
return buf.toString("UTF-8");11.Using inputStream.read() and StringBuilder (JDK). Warning: This solution has problems with Unicode, for example with Russian text (works correctly only with non-Unicode text)
StringBuilder sb = new StringBuilder();
for (int ch; (ch = inputStream.read()) != -1; ) {
sb.append((char) ch);
}
return sb.toString();Warning:
Solutions 4, 5 and 9 convert different line breaks to one.
Solution 11 can’t work correctly with Unicode text
