Manipulating a bytearray stream

Question

I read the following string from command line(example):

abcgefgh0111010111100000

I process this as a stream to arrive at the first position which is a binary( in this case it is position 9). The code is as follows:

String s=args[0];
    ByteArrayInputStream  bis=new ByteArrayInputStream(s.getBytes());
    int c;
    int pos=0;
    while((c=bis.read())>0)
    {
        if(((char)c)=='0' || ((char)c)=='1') break;
        pos++;
    }

bis.mark(pos-1);\\this does not help
    bis.reset();\\this does not help either
    System.out.println("Data begins from : " + pos);
    byte[] arr=new byte[3];
    try{
    bis.read(arr);
    System.out.println(new String(arr));
    }catch(Exception x){}

Now the Arraystream would start reading from position 10('1').
How do I make it recede back by one position to actually start reading again from the first binary digit('0') at position 9.
bis.mark(pos-1) or reset does not help.

Answer 1

Follow bis.mark(pos-1), with bis.reset().

reset() will position the stream's read cursor at the last marked position (pos-1 in this case.)

From doc:

Resets the buffer to the marked position. The marked position is 0 unless another position was marked or an offset was specified in the constructor.

Rewrite your loop like so:

String s = "abcgefgh0111010111100000";
ByteArrayInputStream bis = new ByteArrayInputStream(s.getBytes());
int c;
int pos = 0;
while (true) {
    bis.mark(10);
    if ((c = bis.read()) > 0) {
        if (((char) c) == '0' || ((char) c) == '1')
            break;
        pos++;
    } else
        break;
}
bis.reset();// this does not help either
System.out.println("Data begins from : " + pos);
byte[] arr = new byte[3];
try {
    bis.read(arr);
    System.out.println(new String(arr));
} catch (Exception x) {
}

This code stores the position of the last read byte. Your code wasn't working before because it was storing the position after the byte you wanted was read.