In this quick tutorial we’re going to convert a Reader into a String using plain Java, Guava and the Apache Commons IO library.
This article is part of the “Java – Back to Basic” series here on Baeldung.
1. With Java
Let’s start with a simple Java solution that reads characters sequentially from the Reader:
@Test
public void givenUsingPlainJava_whenConvertingReaderIntoStringV1_thenCorrect()
throws IOException {
StringReader reader = new StringReader("text");
int intValueOfChar;
String targetString = "";
while ((intValueOfChar = reader.read()) != -1) {
targetString += (char) intValueOfChar;
}
reader.close();
}
If there is a lot of content to read, a bulk-read solution will work better:
@Test
public void givenUsingPlainJava_whenConvertingReaderIntoStringV2_thenCorrect()
throws IOException {
Reader initialReader = new StringReader("text");
char[] arr = new char[8 * 1024];
StringBuilder buffer = new StringBuilder();
int numCharsRead;
while ((numCharsRead = initialReader.read(arr, 0, arr.length)) != -1) {
buffer.append(arr, 0, numCharsRead);
}
initialReader.close();
String targetString = buffer.toString();
}
2. With Guava
Guava provides a utility that can do the conversion directly:
@Test
public void givenUsingGuava_whenConvertingReaderIntoString_thenCorrect()
throws IOException {
Reader initialReader = CharSource.wrap("With Google Guava").openStream();
String targetString = CharStreams.toString(initialReader);
initialReader.close();
}
3. With Commons IO
Same with Apache Commons IO – there is an IO utility capable of performing the direct conversion:
@Test
public void givenUsingCommonsIO_whenConvertingReaderIntoString_thenCorrect()
throws IOException {
Reader initialReader = new StringReader("With Apache Commons");
String targetString = IOUtils.toString(initialReader);
initialReader.close();
}
And there you have it – 4 ways of transforming a Reader into a plain String. Make sure to check out the sample over on GitHub.
