FULL PRODUCT VERSION :
$ java -version
java version "1.8.0_77"
Java(TM) SE Runtime Environment (build 1.8.0_77-b03)
Java HotSpot(TM) 64-Bit Server VM (build 25.77-b03, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
$ uname -a
Darwin jfitzpat-mbpr15.xxxxxxxx.com 14.3.0 Darwin Kernel Version 14.3.0: Mon Mar 23 20:23:44 PDT 2015; root:xnu-2782.20.48~8/RELEASE_X86_64 x86_64

A DESCRIPTION OF THE PROBLEM :
The java.util.Scanner class can be used to tokenize input for an arbitrary input stream. In some cases a read operation may only read 0 bytes but then later read more than 0 bytes, e.g. if input is coming from the network. On reading 0 bytes, it appears that java.util.Scanner.hasNext() incorrectly returns false whereas I would expect this to occur only in the case where the end of the input stream has been reached.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Put the contents of the following source in a file called "ScannerHasNextBug.java".

import java.io.IOException;
import java.io.InputStream;
import java.util.Scanner;

public class ScannerHasNextBug {

    public static void main(String[] args) {
        InputStream inputStream = new InputStream() {
            private boolean firstRead = true;

            @Override
            public int read() throws IOException {
                throw new RuntimeException("Not supported");
            }

            @Override
            public int read(byte[] b, int offset, int length) {
                if (firstRead) {
                    firstRead = false;
                    return 0;
                }
                
                b[offset] = 'A';
                
                return 1;
            }
        };

        try (Scanner scanner = new Scanner(inputStream)) {
            System.out.println(scanner.hasNext());
        }
    }
}

mkdir classes
javac -d ./classes ScannerHasNextBug.java
java -cp ./classes ScannerHasNextBug

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
I expect the output of the above program to be "true".
ACTUAL -
The actual output of the above program is "false".

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
See section on "Steps to Reproduce".
---------- END SOURCE ----------