Java StringReader reads beyond input. Is this a bug or expected behavior? [closed]

Question

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Closed 8 years ago.

Try this code -

import java.io.StringReader;

public class StringReaderTest
{
    public static void main(String[] args) throws Exception
    {
        String sampleString = "abcdefg";
        StringReader reader = new StringReader(sampleString);

        for(int i=0; i<40; i++)
        {
            char c = (char) reader.read();
            System.out.print(c);
        }
    }
}

The output is -

abcdefg?????????????????????????????????

So the reader actually read past the end of the input. I was under the impression that it should have thrown an exception when it tried to read beyond "g", but it did not. It instead returned a "?" character. Is this a bug or is this expected behavior?

Answer 1

The documentation is quite clear in this case:

StringReader.read()

Returns: The character read, or -1 if the end of the stream has been reached

Answer 2

According to http://docs.oracle.com/javase/1.4.2/docs/api/java/io/StringReader.html#read%28%29 StringReader.Read() returns -1 if the end of the stream has been reached. It doesn't throw an IOException unless there's some other sort of error.