JSONTokener

public class JSONTokener extends Object

Parses a JSON (RFC 4627) encoded string into the corresponding object. Most clients of this class will use only need the constructor and nextValue() method. Example usage:

 String json = "{"
         + "  \"query\": \"Pizza\", "
         + "  \"locations\": [ 94043, 90210 ] "
         + "}";

 JSONObject object = (JSONObject) new JSONTokener(json).nextValue();
 String query = object.getString("query");
 JSONArray locations = object.getJSONArray("locations");

For best interoperability and performance use JSON that complies with RFC 4627, such as that generated by JSONStringer. For legacy reasons this parser is lenient, so a successful parse does not indicate that the input string was valid JSON. All of the following syntax errors will be ignored:

  • End of line comments starting with // or # and ending with a newline character.
  • C-style comments starting with /* and ending with */. Such comments may not be nested.
  • Strings that are unquoted or 'single quoted'.
  • Hexadecimal integers prefixed with 0x or 0X.
  • Octal integers prefixed with 0.
  • Array elements separated by ;.
  • Unnecessary array separators. These are interpreted as if null was the omitted value.
  • Key-value pairs separated by = or =>.
  • Key-value pairs separated by ;.

Each tokener may be used to parse a single JSON string. Instances of this class are not thread safe. Although this class is nonfinal, it was not designed for inheritance and should not be subclassed. In particular, self-use by overrideable methods is not specified. See Effective Java Item 17, "Design and Document or inheritance or else prohibit it" for further information.

Public Constructor Summary

JSONTokener(String in)

Public Method Summary

void
back()
Unreads the most recent character of input.
static int
dehexchar(char hex)
Returns the integer [0..15] value for the given hex character, or -1 for non-hex input.
boolean
more()
Returns true until the input has been exhausted.
char
next()
Returns the next available character, or the null character '\0' if all input has been exhausted.
char
next(char c)
Returns the next available character if it equals c.
String
next(int length)
Returns the next length characters of the input.
char
nextClean()
Returns the next character that is not whitespace and does not belong to a comment.
String
nextString(char quote)
Returns the string up to but not including quote, unescaping any character escape sequences encountered along the way.
String
nextTo(String excluded)
Returns the trimmed string holding the characters up to but not including the first of:
  • any character in excluded
  • a newline character '\n'
  • a carriage return '\r'

The returned string shares its backing character array with this tokener's input string.

String
nextTo(char excluded)
Equivalent to nextTo(String.valueOf(excluded)).
Object
nextValue()
Returns the next value from the input.
void
skipPast(String thru)
Advances past all input up to and including the next occurrence of thru.
char
skipTo(char to)
Advances past all input up to but not including the next occurrence of to.
JSONException
syntaxError(String message)
Returns an exception containing the given message plus the current position and the entire input string.
String
toString()
Returns the current position and the entire input string.

Inherited Method Summary

Public Constructors

public JSONTokener (String in)

Parameters
in JSON encoded string. Null is not permitted and will yield a tokener that throws NullPointerExceptions when methods are called.

Public Methods

public void back ()

Unreads the most recent character of input. If no input characters have been read, the input is unchanged.

public static int dehexchar (char hex)

Returns the integer [0..15] value for the given hex character, or -1 for non-hex input.

Parameters
hex a character in the ranges [0-9], [A-F] or [a-f]. Any other character will yield a -1 result.

public boolean more ()

Returns true until the input has been exhausted.

public char next ()

Returns the next available character, or the null character '\0' if all input has been exhausted. The return value of this method is ambiguous for JSON strings that contain the character '\0'.

public char next (char c)

Returns the next available character if it equals c. Otherwise an exception is thrown.

Parameters
c
Throws
JSONException

public String next (int length)

Returns the next length characters of the input.

The returned string shares its backing character array with this tokener's input string. If a reference to the returned string may be held indefinitely, you should use new String(result) to copy it first to avoid memory leaks.

Parameters
length
Throws
JSONException if the remaining input is not long enough to satisfy this request.

public char nextClean ()

Returns the next character that is not whitespace and does not belong to a comment. If the input is exhausted before such a character can be found, the null character '\0' is returned. The return value of this method is ambiguous for JSON strings that contain the character '\0'.

Throws
JSONException

public String nextString (char quote)

Returns the string up to but not including quote, unescaping any character escape sequences encountered along the way. The opening quote should have already been read. This consumes the closing quote, but does not include it in the returned string.

Parameters
quote either ' or ".
Throws
JSONException

public String nextTo (String excluded)

Returns the trimmed string holding the characters up to but not including the first of:

  • any character in excluded
  • a newline character '\n'
  • a carriage return '\r'

The returned string shares its backing character array with this tokener's input string. If a reference to the returned string may be held indefinitely, you should use new String(result) to copy it first to avoid memory leaks.

Parameters
excluded
Returns
  • a possibly-empty string

public String nextTo (char excluded)

Equivalent to nextTo(String.valueOf(excluded)).

Parameters
excluded

public Object nextValue ()

Returns the next value from the input.

Returns
Throws
JSONException if the input is malformed.

public void skipPast (String thru)

Advances past all input up to and including the next occurrence of thru. If the remaining input doesn't contain thru, the input is exhausted.

Parameters
thru

public char skipTo (char to)

Advances past all input up to but not including the next occurrence of to. If the remaining input doesn't contain to, the input is unchanged.

Parameters
to

public JSONException syntaxError (String message)

Returns an exception containing the given message plus the current position and the entire input string.

Parameters
message

public String toString ()

Returns the current position and the entire input string.