System.arraycopy(boundary, 0, this.boundary, 4, boundary.length);
System.arraycopy(boundary, 0, this.boundary, BOUNDARY_PREFIX.length, boundary.length);
    public void setBoundary(byte[] boundary)        throws IllegalBoundaryException {        if (boundary.length != boundaryLength - 4) {            throw new IllegalBoundaryException(                    "The length of a boundary token can not be changed");        }        System.arraycopy(boundary, 0, this.boundary, 4, boundary.length);    }