How to use

JsonParser

in

org.hjson

/**
 * Reads a JSON value from the given reader.
 * <p>
 * Characters are read in chunks and buffered internally, therefore wrapping an existing reader in
 * an additional <code>BufferedReader</code> does <strong>not</strong> improve reading
 * performance.
 * </p>
 *
 * @param reader the reader to read the JSON value from
 * @return the JSON value that has been read
 * @throws IOException if an I/O error occurs in the reader
 * @throws ParseException if the input is not valid JSON
 */
public static JsonValue readJSON(Reader reader) throws IOException {
 return new JsonParser(reader).parse();
}

JsonValue parse() throws IOException {
 read();
 skipWhiteSpace();
 JsonValue result=readValue();
 skipWhiteSpace();
 if (!isEndOfText()) throw error("Unexpected character");
 return result;
}

private boolean readFraction() throws IOException {
 if (!readIf('.')) {
  return false;
 }
 if (!readDigit()) {
  throw expected("digit");
 }
 while (readDigit()) {
 }
 return true;
}

private void readRequiredChar(char ch) throws IOException {
 if (!readIf(ch)) {
  throw expected("'"+ch+"'");
 }
}

private ParseException expected(String expected) {
 if (isEndOfText()) {
  return error("Unexpected end of input");
 }
 return error("Expected "+expected);
}

private JsonArray readArray() throws IOException {
 read();
 JsonArray array=new JsonArray();
 skipWhiteSpace();
 if (readIf(']')) {
  return array;
 }
 do {
  skipWhiteSpace();
  array.add(readValue());
  skipWhiteSpace();
 } while (readIf(','));
 if (!readIf(']')) {
  throw expected("',' or ']'");
 }
 return array;
}

private JsonValue readValue() throws IOException {
 switch(current) {
  case 'n':
   return readNull();
  case 't':
   return readTrue();
  case 'f':
   return readFalse();
  case '"':
   return readString();
  case '[':
   return readArray();
  case '{':
   return readObject();
  case '-':
  case '0':
  case '1':
  case '2':
  case '3':
  case '4':
  case '5':
  case '6':
  case '7':
  case '8':
  case '9':
   return readNumber();
  default:
   throw expected("value");
 }
}

private JsonValue readNumber() throws IOException {
 startCapture();
 readIf('-');
 int firstDigit=current;
 if (!readDigit()) {
  throw expected("digit");
 }
 if (firstDigit!='0') {
  while (readDigit()) {
  }
 }
 readFraction();
 readExponent();
 return new JsonNumber(Double.parseDouble(endCapture()));
}

private String readStringInternal() throws IOException {
 read();
 startCapture();
 while (current!='"') {
  if (current=='\\') {
   pauseCapture();
   readEscape();
   startCapture();
  } else if (current<0x20) {
   throw expected("valid string character");
  } else {
   read();
  }
 }
 String string=endCapture();
 read();
 return string;
}

private void readEscape() throws IOException {
 read();
 switch(current) {
  case '"':
   char[] hexChars=new char[4];
   for(int i=0; i<4; i++) {
    read();
    if (!isHexDigit()) {
     throw expected("hexadecimal digit");
   break;
  default:
   throw expected("valid escape sequence");
 read();

private void skipWhiteSpace() throws IOException {
 while (isWhiteSpace()) {
  read();
 }
}

private String readName() throws IOException {
 if (current!='"') {
  throw expected("name");
 }
 return readStringInternal();
}

private boolean readDigit() throws IOException {
 if (!isDigit()) {
  return false;
 }
 read();
 return true;
}

private ParseException error(String message) {
 int absIndex=bufferOffset+index;
 int column=absIndex-lineOffset;
 int offset=isEndOfText() ? absIndex : absIndex-1;
 return new ParseException(message, offset, line, column-1);
}

private JsonArray readArray() throws IOException {
 read();
 JsonArray array=new JsonArray();
 skipWhiteSpace();
 if (readIf(']')) {
  return array;
 }
 do {
  skipWhiteSpace();
  array.add(readValue());
  skipWhiteSpace();
 } while (readIf(','));
 if (!readIf(']')) {
  throw expected("',' or ']'");
 }
 return array;
}

private JsonValue readValue() throws IOException {
 switch(current) {
  case 'n':
   return readNull();
  case 't':
   return readTrue();
  case 'f':
   return readFalse();
  case '"':
   return readString();
  case '[':
   return readArray();
  case '{':
   return readObject();
  case '-':
  case '0':
  case '1':
  case '2':
  case '3':
  case '4':
  case '5':
  case '6':
  case '7':
  case '8':
  case '9':
   return readNumber();
  default:
   throw expected("value");
 }
}

private JsonValue readNumber() throws IOException {
 startCapture();
 readIf('-');
 int firstDigit=current;
 if (!readDigit()) {
  throw expected("digit");
 }
 if (firstDigit!='0') {
  while (readDigit()) {
  }
 }
 readFraction();
 readExponent();
 return new JsonNumber(Double.parseDouble(endCapture()));
}

private String readStringInternal() throws IOException {
 read();
 startCapture();
 while (current!='"') {
  if (current=='\\') {
   pauseCapture();
   readEscape();
   startCapture();
  } else if (current<0x20) {
   throw expected("valid string character");
  } else {
   read();
  }
 }
 String string=endCapture();
 read();
 return string;
}

private void readEscape() throws IOException {
 read();
 switch(current) {
  case '"':
   char[] hexChars=new char[4];
   for(int i=0; i<4; i++) {
    read();
    if (!isHexDigit()) {
     throw expected("hexadecimal digit");
   break;
  default:
   throw expected("valid escape sequence");
 read();

private void readRequiredChar(char ch) throws IOException {
 if (!readIf(ch)) {
  throw expected("'"+ch+"'");
 }
}