This happens on Linux machines with the file /proc/sys/kernel/yama/ptrace_scope only, so far.

We're reading the contents of the file using:

String NEW_LINE = System.getProperty("line.separator");
String s = Files.lines(path).collect(Collectors.joining(NEW_LINE));

With JDK8 the contents are correctly returned. With JDK 9 an empty string returned instead.

Following is the output:

$ java -version
java version "1.9.0-ea"
Java(TM) SE Runtime Environment (build 1.9.0-ea-b74)
Java HotSpot(TM) 64-Bit Server VM (build 1.9.0-ea-b74, mixed mode)

$ cat /proc/sys/kernel/yama/ptrace_scope
1

$ java -jar "/home/akulyakh/NetBeansProjects/StreamTest/dist/StreamTest.jar" /proc/sys/kernel/yama/ptrace_scope
Resulting line:

$ java -version
java version "1.8.0_65-ea"
Java(TM) SE Runtime Environment (build 1.8.0_65-ea-b04)
Java HotSpot(TM) 64-Bit Server VM (build 25.65-b01, mixed mode)


java -jar "/home/akulyakh/NetBeansProjects/StreamTest/dist/StreamTest.jar" /proc/sys/kernel/yama/ptrace_scope
Resulting line: 1

The program to read is as follows:

public class StreamTest {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws IOException {
        
        if(args.length < 1) throw new IllegalArgumentException("Please specify path to file");
        
        Path path = Paths.get(args[0]);
        
        if(!Files.exists(path)) throw new IllegalArgumentException("File must exist");
        
        String NEW_LINE = System.getProperty("line.separator");
        String s = Files.lines(path).collect(Collectors.joining(NEW_LINE));
        System.out.println("Lines read from the file: " + s);
    }

}