public static long copyLarge(Reader input, Writer output) throws IOException {
        return copyLarge(input, output, new char[DEFAULT_BUFFER_SIZE]);
    }
Copy chars from a large (over 2GB) <code>Reader</code> to a <code>Writer</code>.
<p>
This method buffers the input internally, so there is no need to use a
<code>BufferedReader</code>.
<p>
The buffer size is given by {@link #DEFAULT_BUFFER_SIZE}.

@param input  the <code>Reader</code> to read from
@param output the <code>Writer</code> to write to
@return the number of characters copied
@throws NullPointerException if the input or output is null
@throws IOException          if an I/O error occurs
@since 1.3
pay-java-common/src/main/java/com/egzosn/pay/common/util/IOUtils.java