RTEditor/src/main/java/com/onegravity/rteditor/utils/io/IOUtils.java
public static char[] toCharArray(InputStream is, Charset encoding)
            throws IOException {
        CharArrayWriter output = new CharArrayWriter();
        copy(is, output, encoding);
        return output.toCharArray();
    }
public static char[] toCharArray(InputStream is, Charset encoding)
            throws IOException {
        CharArrayWriter output = new CharArrayWriter();
        copy(is, output, encoding);
        return output.toCharArray();
    }
Get the contents of an <code>InputStream</code> as a character array
using the specified character encoding.
<p/>
This method buffers the input internally, so there is no need to use a
<code>BufferedInputStream</code>.

@param is       the <code>InputStream</code> to read from
@param encoding the encoding to use, null means platform default
@return the requested character array
@throws NullPointerException if the input is null
@throws IOException          if an I/O error occurs
@since 2.3