How do I convert a StringReader to a String?

Or using CharStreams from Googles Guava library:

CharStreams.toString(stringReader);

If you prefer not to use external libraries:

 Scanner scanner = new Scanner(reader).useDelimiter("\\A");
 String str = scanner.hasNext() ? scanner.next() : "";

The reason for the hasNext() check is that next() explodes with a NoSuchElementException if the reader wraps a blank (zero-length) string.

The StringReader's toString method does not return the StringReader internal buffers.

You'll need to read from the StringReader to get this.

I recommend using the overload of read which accepts a character array. Bulk reads are faster than single character reads.

ie.

//use string builder to avoid unnecessary string creation.
StringBuilder builder = new StringBuilder();
int charsRead = -1;
char[] chars = new char[100];
do{
    charsRead = reader.read(chars,0,chars.length);
    //if we have valid chars, append them to end of string.
    if(charsRead>0)
        builder.append(chars,0,charsRead);
}while(charsRead>0);
String stringReadFromReader = builder.toString();
System.out.println("String read = "+stringReadFromReader);

import org.apache.commons.io.IOUtils;

String string = IOUtils.toString(reader);