If no mark has been set, then the value of mark is the offset passed to the constructor (or 0 if the offset was not supplied).

since: JDK1.1 -

 public ByteArrayInputStream(byte[] buf) 
{
        this.buf = buf;
        this.pos = 0;
        this.count = buf.length;
}

Creates a ByteArrayInputStream so that it uses buf as its buffer array. The buffer array is not copied. The initial value of pos is 0 and the initial value of count is the length of buf.

Parameters:

buf - the input buffer.

 public ByteArrayInputStream(byte[] buf,
    int offset,
    int length) 
{
        this.buf = buf;
        this.pos = offset;
        this.count = Math.min(offset + length, buf.length);
        this.mark = offset;
}

Creates ByteArrayInputStream that uses buf as its buffer array. The initial value of pos is offset and the initial value of count is the minimum of offset+length and buf.length. The buffer array is not copied. The buffer's mark is set to the specified offset.

Parameters:

buf - the input buffer.

offset - the offset in the buffer of the first byte to read.

length - the maximum number of bytes to read from the buffer.

 public synchronized int available() 
{
        return count - pos;
}

Returns the number of remaining bytes that can be read (or skipped over) from this input stream.

The value returned is count - pos, which is the number of bytes remaining to be read from the input buffer.

 public  void close() throws IOException 
{

}

Closing a ByteArrayInputStream has no effect. The methods in this class can be called after the stream has been closed without generating an IOException.

 public  void mark(int readAheadLimit) 
{
        mark = pos;
}

Set the current marked position in the stream. ByteArrayInputStream objects are marked at position zero by default when constructed. They may be marked at another position within the buffer by this method.

If no mark has been set, then the value of the mark is the offset passed to the constructor (or 0 if the offset was not supplied).

Note: The readAheadLimit for this class has no meaning.

 public boolean markSupported() 
{
        return true;
}

Tests if this InputStream supports mark/reset. The markSupported method of ByteArrayInputStream always returns true.

 public synchronized int read() 
{
        return (pos <  count) ? (buf[pos++] & 0xff) : -1;
}

Reads the next byte of data from this input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned.

This read method cannot block.

 public synchronized int read(byte[] b,
    int off,
    int len) 
{
        if (b == null) {
            throw new NullPointerException();
        } else if (off <  0 || len <  0 || len  > b.length - off) {
            throw new IndexOutOfBoundsException();
        }
        if (pos  >= count) {
            return -1;
        }
        int avail = count - pos;
        if (len  > avail) {
            len = avail;
        }
        if (len < = 0) {
            return 0;
        }
        System.arraycopy(buf, pos, b, off, len);
        pos += len;
        return len;
}

Reads up to len bytes of data into an array of bytes from this input stream. If pos equals count, then -1 is returned to indicate end of file. Otherwise, the number k of bytes read is equal to the smaller of len and count-pos. If k is positive, then bytes buf[pos] through buf[pos+k-1] are copied into b[off] through b[off+k-1] in the manner performed by System.arraycopy. The value k is added into pos and k is returned.

This read method cannot block.

 public synchronized  void reset() 
{
        pos = mark;
}

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.

 public synchronized long skip(long n) 
{
        long k = count - pos;
        if (n <  k) {
            k = n <  0 ? 0 : n;
        }
        pos += k;
        return k;
}

Skips n bytes of input from this input stream. Fewer bytes might be skipped if the end of the input stream is reached. The actual number k of bytes to be skipped is equal to the smaller of n and count-pos. The value k is added into pos and k is returned.