Java：输入流中的垃圾

Question

I worte a small java function that calls another Java program and displays its input.

private static void call() throws Exception 
{
    int  line;                             
    ///Other stuff here
    Process p2= Runtime.getRuntime().exec("java SelfModifying");
    InputStream is = p2.getInputStream();
    //p.waitFor();
    while ((line = is.read()) != -1) {
        System.out.println("result: " + line);
    }       
    Runtime.getRuntime().exit(0);
}

The prorgam that gests called is supposed to return a single int value: '10'.
Instead, I get 4 lines: result: 49 result: 48 result: 13 result: 10

Where do the three other values come from? They are deterministic but seem to come from the input. When I run the program on its own it does not return these 3 lines.

Answer 1

You're reading individual bytes from the stream:

• 49 is ASCII '1' ;
• 48 is ASCII '0' ;
• 13 is ASCII '\\r' ;
• 10 is ASCII '\\n' .

So the contents of the file is 10\\r\\n (10, followed by a windows newline).

You should wrap is in a scanner:

Scanner scanner = new Scanner(is, "UTF-8");
System.out.println(scanner.nextInt());