public String encode(String content, int start, int end) {
	StringBuilder sgml = new StringBuilder();
	char chr, chr2;
	int ord = 0;

	for (int i = 0; i < content.length(); i++) {
		chr = content.charAt(i);
		ord = (int) chr;
		if ( (int) chr > 55296 || (int) chr < 57343 ) {
			if ( (int) chr > 55296 && (int) chr < 56319 ) {
				chr2 = content.charAt(i+1);
				if ( (int) chr2 > 56320 && (int) chr < 57343) {
					ord = (int) ((int) (chr & 1023) << 10) + (int) (chr2 & 1023) + 65536;
					i = i + 1;
				} else {
					//error
				}
			} else {
				//error
			}
		}
		if (start <= ord && ord <= end) {
			sgml.append(prefix + ord + suffix);
		} else {
			sgml.append(chr);
		}
	}
	return sgml.toString();		
}

public String decode(String sgml) {
	StringBuilder content = new StringBuilder();
	StringBuilder buffer  = new StringBuilder();
	int ord = 0, chr = 0, status = 0;

	for (int i = 0; i < sgml.length(); i++) {
		ord = (int)sgml.charAt(i);

		// & 일 경우
		if (ord == 38) {
			status = 1;
			buffer.append((char) ord);
		// # 일 경우
		} else if (status == 1 && ord == 35) {
			status = 2;
			buffer.append((char) ord);
		// 0-9 일 경우
		} else if ((status == 2 || status == 3) && ( 47 < ord  && ord < 58 ) ) {
			status = 3;
			buffer.append((char) ord);
		// ; 일 경우
		} else if (status == 3 && ord == 59 ) {
			status = 0;
			chr = Integer.parseInt(buffer.substring(2, buffer.length()));
			if ( chr < 65536 ) {
				content.append((char) chr);
			} else {
				chr = chr - 65536;
				content.append((char) ((chr >> 10) | 55296));
				content.append((char) ((chr & 1023) | 56320));
			}
			buffer.delete(0, buffer.length());
		// 아무것도 아닐경우
		} else {
			status = 0;
			content.append(buffer);
			buffer.delete(0, buffer.length());
		}
	}
	
	return content.toString();
}