Class JSONObject
JSONObjects
, JSONArrays
, Strings,
Booleans, Integers, Longs, Doubles or NULL
. Values may not be null
,
NaNs
, infinities
, or of any type not
listed here.
This class can coerce values to another type when requested.
- When the requested type is a boolean, strings will be coerced using a case-insensitive comparison to "true" and "false".
- When the requested type is a double, other
Number
types will be coerced usingdoubleValue
. Strings that can be coerced usingDouble.valueOf(String)
will be. - When the requested type is an int, other
Number
types will be coerced usingintValue
. Strings that can be coerced usingDouble.valueOf(String)
will be, and then cast to int. - When the requested type is a long, other
Number
types will be coerced usinglongValue
. Strings that can be coerced usingDouble.valueOf(String)
will be, and then cast to long. This two-step conversion is lossy for very large values. For example, the string "9223372036854775806" yields the long 9223372036854775807. - When the requested type is a String, other non-null values will be coerced using
String.valueOf(Object)
. Although null cannot be coerced, the sentinel valueNULL
is coerced to the string "null".
This class can look up both mandatory and optional values:
- Use
getType()
to retrieve a mandatory value. This fails with aJSONException
if the requested name has no value or if the value cannot be coerced to the requested type. - Use
optType()
to retrieve an optional value. This returns a system- or user-supplied default if the requested name has no value or if the value cannot be coerced to the requested type.
Warning: this class represents null in two incompatible ways: the
standard Java null
reference, and the sentinel value NULL
.
In particular, calling put(name, null)
removes the named entry from the object
but put(name, JSONObject.NULL)
stores an entry whose value is
JSONObject.NULL
.
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.
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Field Summary
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Constructor Summary
ConstructorDescriptionCreates aJSONObject
with no name/value mappings.JSONObject
(String json) Creates a newJSONObject
with name/value mappings from the JSON string.JSONObject
(Map copyFrom) Creates a newJSONObject
by copying all name/value mappings from the given map.JSONObject
(JSONObject copyFrom, String[] names) Creates a newJSONObject
by copying mappings for the listed names from the given object.JSONObject
(JSONTokener readFrom) Creates a newJSONObject
with name/value mappings from the next object in the tokener. -
Method Summary
Modifier and TypeMethodDescriptionaccumulate
(String name, Object value) Appendsvalue
to the array already mapped toname
.Returns the value mapped byname
.boolean
getBoolean
(String name) Returns the value mapped byname
if it exists and is a boolean or can be coerced to a boolean.double
Returns the value mapped byname
if it exists and is a double or can be coerced to a double.int
Returns the value mapped byname
if it exists and is an int or can be coerced to an int.getJSONArray
(String name) Returns the value mapped byname
if it exists and is aJSONArray
.getJSONObject
(String name) Returns the value mapped byname
if it exists and is aJSONObject
.long
Returns the value mapped byname
if it exists and is a long or can be coerced to a long.Returns the value mapped byname
if it exists, coercing it if necessary.boolean
Returns true if this object has a mapping forname
.boolean
Returns true if this object has no mapping forname
or if it has a mapping whose value isNULL
.keys()
Returns an iterator of theString
names in this object.int
length()
Returns the number of name/value mappings in this object.names()
Returns an array containing the string names in this object.static String
numberToString
(Number number) Encodes the number as a JSON string.Returns the value mapped byname
, or null if no such mapping exists.boolean
optBoolean
(String name) Returns the value mapped byname
if it exists and is a boolean or can be coerced to a boolean.boolean
optBoolean
(String name, boolean fallback) Returns the value mapped byname
if it exists and is a boolean or can be coerced to a boolean.double
Returns the value mapped byname
if it exists and is a double or can be coerced to a double.double
Returns the value mapped byname
if it exists and is a double or can be coerced to a double.int
Returns the value mapped byname
if it exists and is an int or can be coerced to an int.int
Returns the value mapped byname
if it exists and is an int or can be coerced to an int.optJSONArray
(String name) Returns the value mapped byname
if it exists and is aJSONArray
.optJSONObject
(String name) Returns the value mapped byname
if it exists and is aJSONObject
.long
Returns the value mapped byname
if it exists and is a long or can be coerced to a long.long
Returns the value mapped byname
if it exists and is a long or can be coerced to a long.Returns the value mapped byname
if it exists, coercing it if necessary.Returns the value mapped byname
if it exists, coercing it if necessary.Mapsname
tovalue
, clobbering any existing name/value mapping with the same name.Mapsname
tovalue
, clobbering any existing name/value mapping with the same name.Mapsname
tovalue
, clobbering any existing name/value mapping with the same name.Mapsname
tovalue
, clobbering any existing name/value mapping with the same name.Mapsname
tovalue
, clobbering any existing name/value mapping with the same name.Equivalent toput(name, value)
when both parameters are non-null; does nothing otherwise.static String
Encodesdata
as a JSON string.Removes the named mapping if it exists; does nothing otherwise.toJSONArray
(JSONArray names) Returns an array with the values corresponding tonames
.toString()
Encodes this object as a compact JSON string, such as:toString
(int indentSpaces) Encodes this object as a human-readable JSON string for debugging, such as:static Object
Wraps the given object if necessary.
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Field Details
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NULL
A sentinel value used to explicitly define a name with no value. Unlikenull
, names with this value:- show up in the
names()
array - show up in the
keys()
iterator - return
true
forhas(String)
- do not throw on
get(String)
- are included in the encoded JSON string.
This value violates the general contract of
Object.equals(java.lang.Object)
by returning true when compared tonull
. ItstoString()
method returns "null". - show up in the
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Constructor Details
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JSONObject
public JSONObject()Creates aJSONObject
with no name/value mappings. -
JSONObject
Creates a newJSONObject
by copying all name/value mappings from the given map.- Parameters:
copyFrom
- a map whose keys are of typeString
and whose values are of supported types.- Throws:
NullPointerException
- if any of the map's keys are null.
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JSONObject
Creates a newJSONObject
with name/value mappings from the next object in the tokener.- Parameters:
readFrom
- a tokener whose nextValue() method will yield aJSONObject
.- Throws:
JSONException
- if the parse fails or doesn't yield aJSONObject
.
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JSONObject
Creates a newJSONObject
with name/value mappings from the JSON string.- Parameters:
json
- a JSON-encoded string containing an object.- Throws:
JSONException
- if the parse fails or doesn't yield aJSONObject
.
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JSONObject
Creates a newJSONObject
by copying mappings for the listed names from the given object. Names that aren't present incopyFrom
will be skipped.- Parameters:
copyFrom
- the sourcenames
- the property names- Throws:
JSONException
- if an error occurs
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Method Details
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length
public int length()Returns the number of name/value mappings in this object.- Returns:
- the number of name/value mappings in this object
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put
Mapsname
tovalue
, clobbering any existing name/value mapping with the same name.- Parameters:
name
- the name of the propertyvalue
- the value of the property- Returns:
- this object.
- Throws:
JSONException
- if an error occurs
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put
Mapsname
tovalue
, clobbering any existing name/value mapping with the same name.- Parameters:
name
- the name of the propertyvalue
- a finite value. May not beNaNs
orinfinities
.- Returns:
- this object.
- Throws:
JSONException
- if an error occurs
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put
Mapsname
tovalue
, clobbering any existing name/value mapping with the same name.- Parameters:
name
- the name of the propertyvalue
- the value of the property- Returns:
- this object.
- Throws:
JSONException
- if an error occurs
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put
Mapsname
tovalue
, clobbering any existing name/value mapping with the same name.- Parameters:
name
- the name of the propertyvalue
- the value of the property- Returns:
- this object.
- Throws:
JSONException
- if an error occurs
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put
Mapsname
tovalue
, clobbering any existing name/value mapping with the same name. If the value isnull
, any existing mapping forname
is removed.- Parameters:
name
- the name of the propertyvalue
- aJSONObject
,JSONArray
, String, Boolean, Integer, Long, Double,NULL
, ornull
. May not beNaNs
orinfinities
.- Returns:
- this object.
- Throws:
JSONException
- if an error occurs
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putOpt
Equivalent toput(name, value)
when both parameters are non-null; does nothing otherwise.- Parameters:
name
- the name of the propertyvalue
- the value of the property- Returns:
- this object.
- Throws:
JSONException
- if an error occurs
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accumulate
Appendsvalue
to the array already mapped toname
. If this object has no mapping forname
, this inserts a new mapping. If the mapping exists but its value is not an array, the existing and new values are inserted in order into a new array which is itself mapped toname
. In aggregate, this allows values to be added to a mapping one at a time.- Parameters:
name
- the name of the propertyvalue
- aJSONObject
,JSONArray
, String, Boolean, Integer, Long, Double,NULL
or null. May not beNaNs
orinfinities
.- Returns:
- this object.
- Throws:
JSONException
- if an error occurs
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remove
Removes the named mapping if it exists; does nothing otherwise.- Parameters:
name
- the name of the property- Returns:
- the value previously mapped by
name
, or null if there was no such mapping.
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isNull
Returns true if this object has no mapping forname
or if it has a mapping whose value isNULL
.- Parameters:
name
- the name of the property- Returns:
- true if this object has no mapping for
name
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has
Returns true if this object has a mapping forname
. The mapping may beNULL
.- Parameters:
name
- the name of the property- Returns:
- true if this object has a mapping for
name
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get
Returns the value mapped byname
.- Parameters:
name
- the name of the property- Returns:
- the value
- Throws:
JSONException
- if no such mapping exists.
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opt
Returns the value mapped byname
, or null if no such mapping exists.- Parameters:
name
- the name of the property- Returns:
- the value or
null
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getBoolean
Returns the value mapped byname
if it exists and is a boolean or can be coerced to a boolean.- Parameters:
name
- the name of the property- Returns:
- the value
- Throws:
JSONException
- if the mapping doesn't exist or cannot be coerced to a boolean.
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optBoolean
Returns the value mapped byname
if it exists and is a boolean or can be coerced to a boolean. Returns false otherwise.- Parameters:
name
- the name of the property- Returns:
- the value or
null
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optBoolean
Returns the value mapped byname
if it exists and is a boolean or can be coerced to a boolean. Returnsfallback
otherwise.- Parameters:
name
- the name of the propertyfallback
- a fallback value- Returns:
- the value or
fallback
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getDouble
Returns the value mapped byname
if it exists and is a double or can be coerced to a double.- Parameters:
name
- the name of the property- Returns:
- the value
- Throws:
JSONException
- if the mapping doesn't exist or cannot be coerced to a double.
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optDouble
Returns the value mapped byname
if it exists and is a double or can be coerced to a double. ReturnsNaN
otherwise.- Parameters:
name
- the name of the property- Returns:
- the value or
NaN
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optDouble
Returns the value mapped byname
if it exists and is a double or can be coerced to a double. Returnsfallback
otherwise.- Parameters:
name
- the name of the propertyfallback
- a fallback value- Returns:
- the value or
fallback
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getInt
Returns the value mapped byname
if it exists and is an int or can be coerced to an int.- Parameters:
name
- the name of the property- Returns:
- the value
- Throws:
JSONException
- if the mapping doesn't exist or cannot be coerced to an int.
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optInt
Returns the value mapped byname
if it exists and is an int or can be coerced to an int. Returns 0 otherwise.- Parameters:
name
- the name of the property- Returns:
- the value of
0
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optInt
Returns the value mapped byname
if it exists and is an int or can be coerced to an int. Returnsfallback
otherwise.- Parameters:
name
- the name of the propertyfallback
- a fallback value- Returns:
- the value or
fallback
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getLong
Returns the value mapped byname
if it exists and is a long or can be coerced to a long. Note that JSON represents numbers as doubles, so this is lossy; use strings to transfer numbers over JSON.- Parameters:
name
- the name of the property- Returns:
- the value
- Throws:
JSONException
- if the mapping doesn't exist or cannot be coerced to a long.
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optLong
Returns the value mapped byname
if it exists and is a long or can be coerced to a long. Returns 0 otherwise. Note that JSON represents numbers as doubles, so this is lossy; use strings to transfer numbers via JSON.- Parameters:
name
- the name of the property- Returns:
- the value or
0L
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optLong
Returns the value mapped byname
if it exists and is a long or can be coerced to a long. Returnsfallback
otherwise. Note that JSON represents numbers as doubles, so this is lossy; use strings to transfer numbers over JSON.- Parameters:
name
- the name of the propertyfallback
- a fallback value- Returns:
- the value or
fallback
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getString
Returns the value mapped byname
if it exists, coercing it if necessary.- Parameters:
name
- the name of the property- Returns:
- the value
- Throws:
JSONException
- if no such mapping exists.
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optString
Returns the value mapped byname
if it exists, coercing it if necessary. Returns the empty string if no such mapping exists.- Parameters:
name
- the name of the property- Returns:
- the value or an empty string
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optString
Returns the value mapped byname
if it exists, coercing it if necessary. Returnsfallback
if no such mapping exists.- Parameters:
name
- the name of the propertyfallback
- a fallback value- Returns:
- the value or
fallback
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getJSONArray
Returns the value mapped byname
if it exists and is aJSONArray
.- Parameters:
name
- the name of the property- Returns:
- the value
- Throws:
JSONException
- if the mapping doesn't exist or is not aJSONArray
.
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optJSONArray
Returns the value mapped byname
if it exists and is aJSONArray
. Returns null otherwise.- Parameters:
name
- the name of the property- Returns:
- the value or
null
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getJSONObject
Returns the value mapped byname
if it exists and is aJSONObject
.- Parameters:
name
- the name of the property- Returns:
- the value
- Throws:
JSONException
- if the mapping doesn't exist or is not aJSONObject
.
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optJSONObject
Returns the value mapped byname
if it exists and is aJSONObject
. Returns null otherwise.- Parameters:
name
- the name of the property- Returns:
- the value or
null
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toJSONArray
Returns an array with the values corresponding tonames
. The array contains null for names that aren't mapped. This method returns null ifnames
is either null or empty.- Parameters:
names
- the names of the properties- Returns:
- the array
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keys
Returns an iterator of theString
names in this object. The returned iterator supportsremove
, which will remove the corresponding mapping from this object. If this object is modified after the iterator is returned, the iterator's behavior is undefined. The order of the keys is undefined.- Returns:
- the keys
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names
Returns an array containing the string names in this object. This method returns null if this object contains no mappings.- Returns:
- the array
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toString
Encodes this object as a compact JSON string, such as:{"query":"Pizza","locations":[94043,90210]}
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toString
Encodes this object as a human-readable JSON string for debugging, such as:{ "query": "Pizza", "locations": [ 94043, 90210 ] }
- Parameters:
indentSpaces
- the number of spaces to indent for each level of nesting.- Returns:
- a string representation of the object.
- Throws:
JSONException
- if an error occurs
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numberToString
Encodes the number as a JSON string.- Parameters:
number
- a finite value. May not beNaNs
orinfinities
.- Returns:
- the encoded value
- Throws:
JSONException
- if an error occurs
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quote
Encodesdata
as a JSON string. This applies quotes and any necessary character escaping.- Parameters:
data
- the string to encode. Null will be interpreted as an empty string.- Returns:
- the quoted value
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wrap
Wraps the given object if necessary.If the object is null or , returns
NULL
. If the object is aJSONArray
orJSONObject
, no wrapping is necessary. If the object isNULL
, no wrapping is necessary. If the object is an array orCollection
, returns an equivalentJSONArray
. If the object is aMap
, returns an equivalentJSONObject
. If the object is a primitive wrapper type orString
, returns the object. Otherwise if the object is from ajava
package, returns the result oftoString
. If wrapping fails, returns null.- Parameters:
o
- the object to wrap- Returns:
- the wrapped object
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