Properties
public
class
Properties
extends Hashtable<Object, Object>
java.lang.Object | |||
↳ | java.util.Dictionary<java.lang.Object, java.lang.Object> | ||
↳ | java.util.Hashtable<java.lang.Object, java.lang.Object> | ||
↳ | java.util.Properties |
The Properties
class represents a persistent set of
properties. The Properties
can be saved to a stream
or loaded from a stream. Each key and its corresponding value in
the property list is a string.
A property list can contain another property list as its "defaults"; this second property list is searched if the property key is not found in the original property list.
Because Properties
inherits from Hashtable
, the
put
and putAll
methods can be applied to a
Properties
object. Their use is strongly discouraged as they
allow the caller to insert entries whose keys or values are not
Strings
. The setProperty
method should be used
instead. If the store
or save
method is called
on a "compromised" Properties
object that contains a
non-String
key or value, the call will fail. Similarly,
the call to the propertyNames
or list
method
will fail if it is called on a "compromised" Properties
object that contains a non-String
key.
The iterators returned by the iterator
method of this class's
"collection views" (that is, entrySet()
, keySet()
, and
values()
) may not fail-fast (unlike the Hashtable implementation).
These iterators are guaranteed to traverse elements as they existed upon
construction exactly once, and may (but are not guaranteed to) reflect any
modifications subsequent to construction.
The load(Reader)
/
store(Writer, String)
methods load and store properties from and to a character based stream
in a simple line-oriented format specified below.
The load(InputStream)
/
store(OutputStream, String)
methods work the same way as the load(Reader)/store(Writer, String) pair, except
the input/output stream is encoded in ISO 8859-1 character encoding.
Characters that cannot be directly represented in this encoding can be written using
Unicode escapes as defined in section {@jls 3.3} of
The Java Language Specification;
only a single 'u' character is allowed in an escape
sequence.
The loadFromXML(java.io.InputStream)
and storeToXML(java.io.OutputStream, java.lang.String, java.lang.String)
methods load and store properties
in a simple XML format. By default the UTF-8 character encoding is used,
however a specific encoding may be specified if required. Implementations
are required to support UTF-8 and UTF-16 and may support other encodings.
An XML properties document has the following DOCTYPE declaration:
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
<?xml version="1.0" encoding="UTF-8"?> <!-- DTD for properties --> <!ELEMENT properties ( comment?, entry* ) > <!ATTLIST properties version CDATA #FIXED "1.0"> <!ELEMENT comment (#PCDATA) > <!ELEMENT entry (#PCDATA) > <!ATTLIST entry key CDATA #REQUIRED>
This class is thread-safe: multiple threads can share a single
Properties
object without the need for external synchronization.
Summary
Fields | |
---|---|
protected
Properties |
defaults
A property list that contains default values for any keys not found in this property list. |
Public constructors | |
---|---|
Properties()
Creates an empty property list with no default values. |
|
Properties(int initialCapacity)
Creates an empty property list with no default values, and with an initial size accommodating the specified number of elements without the need to dynamically resize. |
|
Properties(Properties defaults)
Creates an empty property list with the specified defaults. |
Public methods | |
---|---|
void
|
clear()
Clears this hashtable so that it contains no keys. |
Object
|
clone()
Creates a shallow copy of this hashtable. |
Object
|
compute(Object key, BiFunction<? super Object, ? super Object, ?> remappingFunction)
Attempts to compute a mapping for the specified key and its current
mapped value (or This method will, on a best-effort basis, throw a
|
Object
|
computeIfAbsent(Object key, Function<? super Object, ?> mappingFunction)
If the specified key is not already associated with a value (or is mapped
to This method will, on a best-effort basis, throw a
|
Object
|
computeIfPresent(Object key, BiFunction<? super Object, ? super Object, ?> remappingFunction)
If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value. This method will, on a best-effort basis, throw a
|
boolean
|
contains(Object value)
Tests if some key maps into the specified value in this hashtable. |
boolean
|
containsKey(Object key)
Tests if the specified object is a key in this hashtable. |
boolean
|
containsValue(Object value)
Returns true if this hashtable maps one or more keys to this value. |
Enumeration<Object>
|
elements()
Returns an enumeration of the values in this hashtable. |
Set<Entry<Object, Object>>
|
entrySet()
Returns a |
boolean
|
equals(Object o)
Compares the specified Object with this Map for equality, as per the definition in the Map interface. |
void
|
forEach(BiConsumer<? super Object, ? super Object> action)
Performs the given action for each entry in this map until all entries have been processed or the action throws an exception. |
Object
|
get(Object key)
Returns the value to which the specified key is mapped,
or |
Object
|
getOrDefault(Object key, Object defaultValue)
Returns the value to which the specified key is mapped, or
|
String
|
getProperty(String key, String defaultValue)
Searches for the property with the specified key in this property list. |
String
|
getProperty(String key)
Searches for the property with the specified key in this property list. |
int
|
hashCode()
Returns the hash code value for this Map as per the definition in the Map interface. |
boolean
|
isEmpty()
Tests if this hashtable maps no keys to values. |
Set<Object>
|
keySet()
Returns a |
Enumeration<Object>
|
keys()
Returns an enumeration of the keys in this hashtable. |
void
|
list(PrintWriter out)
Prints this property list out to the specified output stream. |
void
|
list(PrintStream out)
Prints this property list out to the specified output stream. |
void
|
load(Reader reader)
Reads a property list (key and element pairs) from the input character stream in a simple line-oriented format. |
void
|
load(InputStream inStream)
Reads a property list (key and element pairs) from the input byte stream. |
void
|
loadFromXML(InputStream in)
Loads all of the properties represented by the XML document on the specified input stream into this properties table. |
Object
|
merge(Object key, Object value, BiFunction<? super Object, ? super Object, ?> remappingFunction)
If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value. This method will, on a best-effort basis, throw a
|
Enumeration<?>
|
propertyNames()
Returns an enumeration of all the keys in this property list, including distinct keys in the default property list if a key of the same name has not already been found from the main properties list. |
Object
|
put(Object key, Object value)
Maps the specified |
void
|
putAll(Map<?, ?> t)
Copies all of the mappings from the specified map to this hashtable. |
Object
|
putIfAbsent(Object key, Object value)
If the specified key is not already associated with a value (or is mapped
to |
boolean
|
remove(Object key, Object value)
Removes the entry for the specified key only if it is currently mapped to the specified value. |
Object
|
remove(Object key)
Removes the key (and its corresponding value) from this hashtable. |
Object
|
replace(Object key, Object value)
Replaces the entry for the specified key only if it is currently mapped to some value. |
boolean
|
replace(Object key, Object oldValue, Object newValue)
Replaces the entry for the specified key only if currently mapped to the specified value. |
void
|
replaceAll(BiFunction<? super Object, ? super Object, ?> function)
Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception. |
void
|
save(OutputStream out, String comments)
This method was deprecated
in API level 15.
This method does not throw an IOException if an I/O error
occurs while saving the property list. The preferred way to save a
properties list is via the |
Object
|
setProperty(String key, String value)
Calls the |
int
|
size()
Returns the number of keys in this hashtable. |
void
|
store(Writer writer, String comments)
Writes this property list (key and element pairs) in this
|
void
|
store(OutputStream out, String comments)
Writes this property list (key and element pairs) in this
|
void
|
storeToXML(OutputStream os, String comment)
Emits an XML document representing all of the properties contained in this table. |
void
|
storeToXML(OutputStream os, String comment, String encoding)
Emits an XML document representing all of the properties contained in this table, using the specified encoding. |
void
|
storeToXML(OutputStream os, String comment, Charset charset)
Emits an XML document representing all of the properties contained in this table, using the specified encoding. |
Set<String>
|
stringPropertyNames()
Returns an unmodifiable set of keys from this property list where the key and its corresponding value are strings, including distinct keys in the default property list if a key of the same name has not already been found from the main properties list. |
String
|
toString()
Returns a string representation of this |
Collection<Object>
|
values()
Returns a |
Protected methods | |
---|---|
void
|
rehash()
Increases the capacity of and internally reorganizes this hashtable, in order to accommodate and access its entries more efficiently. |
Inherited methods | |
---|---|
Fields
defaults
protected Properties defaults
A property list that contains default values for any keys not found in this property list.
Public constructors
Properties
public Properties ()
Creates an empty property list with no default values.
Implementation Note:
- The initial capacity of a
Properties
object created with this constructor is unspecified.
Properties
public Properties (int initialCapacity)
Creates an empty property list with no default values, and with an initial size accommodating the specified number of elements without the need to dynamically resize.
Parameters | |
---|---|
initialCapacity |
int : the Properties will be sized to
accommodate this many elements |
Throws | |
---|---|
IllegalArgumentException |
if the initial capacity is less than zero. |
Properties
public Properties (Properties defaults)
Creates an empty property list with the specified defaults.
Implementation Note:
- The initial capacity of a
Properties
object created with this constructor is unspecified.
Parameters | |
---|---|
defaults |
Properties : the defaults. |
Public methods
clone
public Object clone ()
Creates a shallow copy of this hashtable. All the structure of the hashtable itself is copied, but the keys and values are not cloned. This is a relatively expensive operation.
Returns | |
---|---|
Object |
a clone of the hashtable |
compute
public Object compute (Object key, BiFunction<? super Object, ? super Object, ?> remappingFunction)
Attempts to compute a mapping for the specified key and its current
mapped value (or null
if there is no current mapping). For
example, to either create or append a String
msg to a value
mapping:
map.compute(key, (k, v) -> (v == null) ? msg : v.concat(msg))
merge()
is often simpler to use for such purposes.)
If the remapping function returns null
, the mapping is removed
(or remains absent if initially absent). If the remapping function
itself throws an (unchecked) exception, the exception is rethrown, and
the current mapping is left unchanged.
The remapping function should not modify this map during computation.
This method will, on a best-effort basis, throw a
ConcurrentModificationException
if the remapping
function modified this map during computation.
Parameters | |
---|---|
key |
Object : key with which the specified value is to be associated |
remappingFunction |
BiFunction : the remapping function to compute a value |
Returns | |
---|---|
Object |
the new value associated with the specified key, or null if none |
computeIfAbsent
public Object computeIfAbsent (Object key, Function<? super Object, ?> mappingFunction)
If the specified key is not already associated with a value (or is mapped
to null
), attempts to compute its value using the given mapping
function and enters it into this map unless null
.
If the mapping function returns null
, no mapping is recorded.
If the mapping function itself throws an (unchecked) exception, the
exception is rethrown, and no mapping is recorded. The most
common usage is to construct a new object serving as an initial
mapped value or memoized result, as in:
map.computeIfAbsent(key, k -> new Value(f(k)));
Or to implement a multi-value map, Map<K,Collection<V>>
,
supporting multiple values per key:
map.computeIfAbsent(key, k -> new HashSet<V>()).add(v);
The mapping function should not modify this map during computation.
This method will, on a best-effort basis, throw a
ConcurrentModificationException
if the mapping
function modified this map during computation.
Parameters | |
---|---|
key |
Object : key with which the specified value is to be associated |
mappingFunction |
Function : the mapping function to compute a value |
Returns | |
---|---|
Object |
the current (existing or computed) value associated with the specified key, or null if the computed value is null |
computeIfPresent
public Object computeIfPresent (Object key, BiFunction<? super Object, ? super Object, ?> remappingFunction)
If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value.
If the remapping function returns null
, the mapping is removed.
If the remapping function itself throws an (unchecked) exception, the
exception is rethrown, and the current mapping is left unchanged.
The remapping function should not modify this map during computation.
This method will, on a best-effort basis, throw a
ConcurrentModificationException
if the remapping
function modified this map during computation.
Parameters | |
---|---|
key |
Object : key with which the specified value is to be associated |
remappingFunction |
BiFunction : the remapping function to compute a value |
Returns | |
---|---|
Object |
the new value associated with the specified key, or null if none |
contains
public boolean contains (Object value)
Tests if some key maps into the specified value in this hashtable.
This operation is more expensive than the containsKey
method.
Note that this method is identical in functionality to
containsValue
, (which is part of the
Map
interface in the collections framework).
Parameters | |
---|---|
value |
Object : a value to search for |
Returns | |
---|---|
boolean |
true if and only if some key maps to the
value argument in this hashtable as
determined by the equals method;
false otherwise. |
containsKey
public boolean containsKey (Object key)
Tests if the specified object is a key in this hashtable.
Parameters | |
---|---|
key |
Object : possible key |
Returns | |
---|---|
boolean |
true if and only if the specified object
is a key in this hashtable, as determined by the
equals method; false otherwise. |
containsValue
public boolean containsValue (Object value)
Returns true if this hashtable maps one or more keys to this value.
Note that this method is identical in functionality to contains
(which predates the Map
interface).
Parameters | |
---|---|
value |
Object : value whose presence in this hashtable is to be tested |
Returns | |
---|---|
boolean |
true if this map maps one or more keys to the
specified value |
elements
public Enumeration<Object> elements ()
Returns an enumeration of the values in this hashtable. Use the Enumeration methods on the returned object to fetch the elements sequentially. If the hashtable is structurally modified while enumerating over the values then the results of enumerating are undefined.
Returns | |
---|---|
Enumeration<Object> |
an enumeration of the values in this hashtable. |
entrySet
public Set<Entry<Object, Object>> entrySet ()
Returns a Set
view of the mappings contained in this map.
The set is backed by the map, so changes to the map are
reflected in the set, and vice-versa. If the map is modified
while an iteration over the set is in progress (except through
the iterator's own remove
operation, or through the
setValue
operation on a map entry returned by the
iterator) the results of the iteration are undefined. The set
supports element removal, which removes the corresponding
mapping from the map, via the Iterator.remove
,
Set.remove
, removeAll
, retainAll
and
clear
operations. It does not support the
add
or addAll
operations.
Returns | |
---|---|
Set<Entry<Object, Object>> |
a set view of the mappings contained in this map |
equals
public boolean equals (Object o)
Compares the specified Object with this Map for equality, as per the definition in the Map interface.
Parameters | |
---|---|
o |
Object : object to be compared for equality with this hashtable |
Returns | |
---|---|
boolean |
true if the specified Object is equal to this Map |
forEach
public void forEach (BiConsumer<? super Object, ? super Object> action)
Performs the given action for each entry in this map until all entries have been processed or the action throws an exception. Unless otherwise specified by the implementing class, actions are performed in the order of entry set iteration (if an iteration order is specified.) Exceptions thrown by the action are relayed to the caller.
Parameters | |
---|---|
action |
BiConsumer : The action to be performed for each entry |
get
public Object get (Object key)
Returns the value to which the specified key is mapped,
or null
if this map contains no mapping for the key.
More formally, if this map contains a mapping from a key
k
to a value v
such that (key.equals(k))
,
then this method returns v
; otherwise it returns
null
. (There can be at most one such mapping.)
Parameters | |
---|---|
key |
Object : the key whose associated value is to be returned |
Returns | |
---|---|
Object |
the value to which the specified key is mapped, or
null if this map contains no mapping for the key |
getOrDefault
public Object getOrDefault (Object key, Object defaultValue)
Returns the value to which the specified key is mapped, or
defaultValue
if this map contains no mapping for the key.
Parameters | |
---|---|
key |
Object : the key whose associated value is to be returned |
defaultValue |
Object : the default mapping of the key |
Returns | |
---|---|
Object |
the value to which the specified key is mapped, or
defaultValue if this map contains no mapping for the key |
getProperty
public String getProperty (String key, String defaultValue)
Searches for the property with the specified key in this property list. If the key is not found in this property list, the default property list, and its defaults, recursively, are then checked. The method returns the default value argument if the property is not found.
Parameters | |
---|---|
key |
String : the hashtable key. |
defaultValue |
String : a default value. |
Returns | |
---|---|
String |
the value in this property list with the specified key value. |
See also:
getProperty
public String getProperty (String key)
Searches for the property with the specified key in this property list.
If the key is not found in this property list, the default property list,
and its defaults, recursively, are then checked. The method returns
null
if the property is not found.
Parameters | |
---|---|
key |
String : the property key. |
Returns | |
---|---|
String |
the value in this property list with the specified key value. |
See also:
hashCode
public int hashCode ()
Returns the hash code value for this Map as per the definition in the Map interface.
Returns | |
---|---|
int |
a hash code value for this object. |
isEmpty
public boolean isEmpty ()
Tests if this hashtable maps no keys to values.
Returns | |
---|---|
boolean |
true if this hashtable maps no keys to values;
false otherwise. |
keySet
public Set<Object> keySet ()
Returns a Set
view of the keys contained in this map.
The set is backed by the map, so changes to the map are
reflected in the set, and vice-versa. If the map is modified
while an iteration over the set is in progress (except through
the iterator's own remove
operation), the results of
the iteration are undefined. The set supports element removal,
which removes the corresponding mapping from the map, via the
Iterator.remove
, Set.remove
,
removeAll
, retainAll
, and clear
operations. It does not support the add
or addAll
operations.
Returns | |
---|---|
Set<Object> |
a set view of the keys contained in this map |
keys
public Enumeration<Object> keys ()
Returns an enumeration of the keys in this hashtable. Use the Enumeration methods on the returned object to fetch the keys sequentially. If the hashtable is structurally modified while enumerating over the keys then the results of enumerating are undefined.
Returns | |
---|---|
Enumeration<Object> |
an enumeration of the keys in this hashtable. |
list
public void list (PrintWriter out)
Prints this property list out to the specified output stream. This method is useful for debugging.
Parameters | |
---|---|
out |
PrintWriter : an output stream. |
Throws | |
---|---|
ClassCastException |
if any key in this property list is not a string. |
list
public void list (PrintStream out)
Prints this property list out to the specified output stream. This method is useful for debugging.
Parameters | |
---|---|
out |
PrintStream : an output stream. |
Throws | |
---|---|
ClassCastException |
if any key in this property list is not a string. |
load
public void load (Reader reader)
Reads a property list (key and element pairs) from the input character stream in a simple line-oriented format.
Properties are processed in terms of lines. There are two
kinds of line, natural lines and logical lines.
A natural line is defined as a line of
characters that is terminated either by a set of line terminator
characters (\n
or \r
or \r\n
)
or by the end of the stream. A natural line may be either a blank line,
a comment line, or hold all or some of a key-element pair. A logical
line holds all the data of a key-element pair, which may be spread
out across several adjacent natural lines by escaping
the line terminator sequence with a backslash character
\
. Note that a comment line cannot be extended
in this manner; every natural line that is a comment must have
its own comment indicator, as described below. Lines are read from
input until the end of the stream is reached.
A natural line that contains only white space characters is
considered blank and is ignored. A comment line has an ASCII
'#'
or '!'
as its first non-white
space character; comment lines are also ignored and do not
encode key-element information. In addition to line
terminators, this format considers the characters space
(' '
, '\u0020'
), tab
('\t'
, '\u0009'
), and form feed
('\f'
, '\u000C'
) to be white
space.
If a logical line is spread across several natural lines, the backslash escaping the line terminator sequence, the line terminator sequence, and any white space at the start of the following line have no affect on the key or element values. The remainder of the discussion of key and element parsing (when loading) will assume all the characters constituting the key and element appear on a single natural line after line continuation characters have been removed. Note that it is not sufficient to only examine the character preceding a line terminator sequence to decide if the line terminator is escaped; there must be an odd number of contiguous backslashes for the line terminator to be escaped. Since the input is processed from left to right, a non-zero even number of 2n contiguous backslashes before a line terminator (or elsewhere) encodes n backslashes after escape processing.
The key contains all of the characters in the line starting
with the first non-white space character and up to, but not
including, the first unescaped '='
,
':'
, or white space character other than a line
terminator. All of these key termination characters may be
included in the key by escaping them with a preceding backslash
character; for example,
\:\=
would be the two-character key ":="
. Line
terminator characters can be included using \r
and
\n
escape sequences. Any white space after the
key is skipped; if the first non-white space character after
the key is '='
or ':'
, then it is
ignored and any white space characters after it are also
skipped. All remaining characters on the line become part of
the associated element string; if there are no remaining
characters, the element is the empty string
""
. Once the raw character sequences
constituting the key and element are identified, escape
processing is performed as described above.
As an example, each of the following three lines specifies the key
"Truth"
and the associated element value
"Beauty"
:
Truth = Beauty Truth:Beauty Truth :Beauty
fruits apple, banana, pear, \ cantaloupe, watermelon, \ kiwi, mango
"fruits"
and the associated element is:
"apple, banana, pear, cantaloupe, watermelon, kiwi, mango"
\
so that a space
will appear after each comma in the final result; the \
,
line terminator, and leading white space on the continuation line are
merely discarded and are not replaced by one or more other
characters.
As a third example, the line:
cheeses
"cheeses"
and the associated
element is the empty string ""
.
Characters in keys and elements can be represented in escape sequences similar to those used for character and string literals (see sections {@jls 3.3} and {@jls 3.10.6} of The Java Language Specification). The differences from the character escape sequences and Unicode escapes used for characters and strings are:
- Octal escapes are not recognized.
- The character sequence
\b
does not represent a backspace character. - The method does not treat a backslash character,
\
, before a non-valid escape character as an error; the backslash is silently dropped. For example, in a Java string the sequence"\z"
would cause a compile time error. In contrast, this method silently drops the backslash. Therefore, this method treats the two character sequence"\b"
as equivalent to the single character'b'
. - Escapes are not necessary for single and double quotes; however, by the rule above, single and double quote characters preceded by a backslash still yield single and double quote characters, respectively.
- Only a single 'u' character is allowed in a Unicode escape sequence.
The specified stream remains open after this method returns.
Parameters | |
---|---|
reader |
Reader : the input character stream. |
Throws | |
---|---|
IOException |
if an error occurred when reading from the input stream. |
IllegalArgumentException |
if a malformed Unicode escape appears in the input. |
NullPointerException |
if reader is null. |
load
public void load (InputStream inStream)
Reads a property list (key and element pairs) from the input
byte stream. The input stream is in a simple line-oriented
format as specified in
load(Reader)
and is assumed to use
the ISO 8859-1 character encoding; that is each byte is one Latin1
character. Characters not in Latin1, and certain special characters,
are represented in keys and elements using Unicode escapes as defined in
section {@jls 3.3} of
The Java Language Specification.
The specified stream remains open after this method returns.
Parameters | |
---|---|
inStream |
InputStream : the input stream. |
Throws | |
---|---|
IOException |
if an error occurred when reading from the input stream. |
IllegalArgumentException |
if the input stream contains a malformed Unicode escape sequence. |
NullPointerException |
if inStream is null. |
loadFromXML
public void loadFromXML (InputStream in)
Loads all of the properties represented by the XML document on the specified input stream into this properties table.
The XML document must have the following DOCTYPE declaration:
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
An implementation is required to read XML documents that use the
"UTF-8
" or "UTF-16
" encoding. An implementation may
support additional encodings.
The specified stream is closed after this method returns.
Parameters | |
---|---|
in |
InputStream : the input stream from which to read the XML document. |
Throws | |
---|---|
IOException |
if reading from the specified input stream
results in an IOException . |
UnsupportedEncodingException |
if the document's encoding declaration can be read and it specifies an encoding that is not supported |
InvalidPropertiesFormatException |
Data on input stream does not constitute a valid XML document with the mandated document type. |
NullPointerException |
if in is null. |
merge
public Object merge (Object key, Object value, BiFunction<? super Object, ? super Object, ?> remappingFunction)
If the specified key is not already associated with a value or is
associated with null, associates it with the given non-null value.
Otherwise, replaces the associated value with the results of the given
remapping function, or removes if the result is null
. This
method may be of use when combining multiple mapped values for a key.
For example, to either create or append a String msg
to a
value mapping:
map.merge(key, msg, String::concat)
If the remapping function returns null
, the mapping is removed.
If the remapping function itself throws an (unchecked) exception, the
exception is rethrown, and the current mapping is left unchanged.
The remapping function should not modify this map during computation.
This method will, on a best-effort basis, throw a
ConcurrentModificationException
if the remapping
function modified this map during computation.
Parameters | |
---|---|
key |
Object : key with which the resulting value is to be associated |
value |
Object : the non-null value to be merged with the existing value
associated with the key or, if no existing value or a null value
is associated with the key, to be associated with the key |
remappingFunction |
BiFunction : the remapping function to recompute a value if
present |
Returns | |
---|---|
Object |
the new value associated with the specified key, or null if no value is associated with the key |
propertyNames
public Enumeration<?> propertyNames ()
Returns an enumeration of all the keys in this property list, including distinct keys in the default property list if a key of the same name has not already been found from the main properties list.
Returns | |
---|---|
Enumeration<?> |
an enumeration of all the keys in this property list, including the keys in the default property list. |
Throws | |
---|---|
ClassCastException |
if any key in this property list is not a string. |
See also:
put
public Object put (Object key, Object value)
Maps the specified key
to the specified
value
in this hashtable. Neither the key nor the
value can be null
.
The value can be retrieved by calling the get
method
with a key that is equal to the original key.
Parameters | |
---|---|
key |
Object : the hashtable key |
value |
Object : the value |
Returns | |
---|---|
Object |
the previous value of the specified key in this hashtable,
or null if it did not have one |
putAll
public void putAll (Map<?, ?> t)
Copies all of the mappings from the specified map to this hashtable. These mappings will replace any mappings that this hashtable had for any of the keys currently in the specified map.
Parameters | |
---|---|
t |
Map : mappings to be stored in this map |
putIfAbsent
public Object putIfAbsent (Object key, Object value)
If the specified key is not already associated with a value (or is mapped
to null
) associates it with the given value and returns
null
, else returns the current value.
Parameters | |
---|---|
key |
Object : key with which the specified value is to be associated |
value |
Object : value to be associated with the specified key |
Returns | |
---|---|
Object |
the previous value associated with the specified key, or
null if there was no mapping for the key.
(A null return can also indicate that the map
previously associated null with the key,
if the implementation supports null values.) |
remove
public boolean remove (Object key, Object value)
Removes the entry for the specified key only if it is currently mapped to the specified value.
Parameters | |
---|---|
key |
Object : key with which the specified value is associated |
value |
Object : value expected to be associated with the specified key |
Returns | |
---|---|
boolean |
true if the value was removed |
remove
public Object remove (Object key)
Removes the key (and its corresponding value) from this hashtable. This method does nothing if the key is not in the hashtable.
Parameters | |
---|---|
key |
Object : the key that needs to be removed |
Returns | |
---|---|
Object |
the value to which the key had been mapped in this hashtable,
or null if the key did not have a mapping |
replace
public Object replace (Object key, Object value)
Replaces the entry for the specified key only if it is currently mapped to some value.
Parameters | |
---|---|
key |
Object : key with which the specified value is associated |
value |
Object : value to be associated with the specified key |
Returns | |
---|---|
Object |
the previous value associated with the specified key, or
null if there was no mapping for the key.
(A null return can also indicate that the map
previously associated null with the key,
if the implementation supports null values.) |
replace
public boolean replace (Object key, Object oldValue, Object newValue)
Replaces the entry for the specified key only if currently mapped to the specified value.
Parameters | |
---|---|
key |
Object : key with which the specified value is associated |
oldValue |
Object : value expected to be associated with the specified key |
newValue |
Object : value to be associated with the specified key |
Returns | |
---|---|
boolean |
true if the value was replaced |
replaceAll
public void replaceAll (BiFunction<? super Object, ? super Object, ?> function)
Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception. Exceptions thrown by the function are relayed to the caller.
Parameters | |
---|---|
function |
BiFunction : the function to apply to each entry |
save
public void save (OutputStream out, String comments)
This method was deprecated
in API level 15.
This method does not throw an IOException if an I/O error
occurs while saving the property list. The preferred way to save a
properties list is via the store(OutputStream out,
String comments)
method or the
storeToXML(OutputStream os, String comment)
method.
Calls the store(OutputStream out, String comments)
method
and suppresses IOExceptions that were thrown.
Parameters | |
---|---|
out |
OutputStream : an output stream. |
comments |
String : a description of the property list. |
Throws | |
---|---|
ClassCastException |
if this Properties object
contains any keys or values that are not
Strings . |
setProperty
public Object setProperty (String key, String value)
Calls the Hashtable
method put
. Provided for
parallelism with the getProperty
method. Enforces use of
strings for property keys and values. The value returned is the
result of the Hashtable
call to put
.
Parameters | |
---|---|
key |
String : the key to be placed into this property list. |
value |
String : the value corresponding to key . |
Returns | |
---|---|
Object |
the previous value of the specified key in this property
list, or null if it did not have one. |
See also:
size
public int size ()
Returns the number of keys in this hashtable.
Returns | |
---|---|
int |
the number of keys in this hashtable. |
store
public void store (Writer writer, String comments)
Writes this property list (key and element pairs) in this
Properties
table to the output character stream in a
format suitable for using the load(Reader)
method.
Properties from the defaults table of this Properties
table (if any) are not written out by this method.
If the comments argument is not null, then an ASCII #
character, the comments string, and a line separator are first written
to the output stream. Thus, the comments
can serve as an
identifying comment. Any one of a line feed ('\n'), a carriage
return ('\r'), or a carriage return followed immediately by a line feed
in comments is replaced by a line separator generated by the Writer
and if the next character in comments is not character #
or
character !
then an ASCII #
is written out
after that line separator.
Next, a comment line is always written, consisting of an ASCII
#
character, the current date and time (as if produced
by the toString
method of Date
for the
current time), and a line separator as generated by the Writer
.
Then every entry in this Properties
table is
written out, one per line. For each entry the key string is
written, then an ASCII =
, then the associated
element string. For the key, all space characters are
written with a preceding \
character. For the
element, leading space characters, but not embedded or trailing
space characters, are written with a preceding \
character. The key and element characters #
,
!
, =
, and :
are written
with a preceding backslash to ensure that they are properly loaded.
After the entries have been written, the output stream is flushed. The output stream remains open after this method returns.
Parameters | |
---|---|
writer |
Writer : an output character stream writer. |
comments |
String : a description of the property list. |
Throws | |
---|---|
IOException |
if writing this property list to the specified
output stream throws an IOException . |
ClassCastException |
if this Properties object
contains any keys or values that are not Strings . |
NullPointerException |
if writer is null. |
store
public void store (OutputStream out, String comments)
Writes this property list (key and element pairs) in this
Properties
table to the output stream in a format suitable
for loading into a Properties
table using the
load(InputStream)
method.
Properties from the defaults table of this Properties
table (if any) are not written out by this method.
This method outputs the comments, properties keys and values in
the same format as specified in
store(Writer)
,
with the following differences:
- The stream is written using the ISO 8859-1 character encoding.
- Characters not in Latin-1 in the comments are written as
\u
xxxx for their appropriate unicode hexadecimal value xxxx. - Characters less than
\u0020
and characters greater than\u007E
in property keys or values are written as\u
xxxx for the appropriate hexadecimal value xxxx.
After the entries have been written, the output stream is flushed. The output stream remains open after this method returns.
Parameters | |
---|---|
out |
OutputStream : an output stream. |
comments |
String : a description of the property list. |
Throws | |
---|---|
IOException |
if writing this property list to the specified
output stream throws an IOException . |
ClassCastException |
if this Properties object
contains any keys or values that are not Strings . |
NullPointerException |
if out is null. |
storeToXML
public void storeToXML (OutputStream os, String comment)
Emits an XML document representing all of the properties contained in this table.
An invocation of this method of the form props.storeToXML(os,
comment)
behaves in exactly the same way as the invocation
props.storeToXML(os, comment, "UTF-8");
.
Parameters | |
---|---|
os |
OutputStream : the output stream on which to emit the XML document. |
comment |
String : a description of the property list, or null
if no comment is desired. |
Throws | |
---|---|
IOException |
if writing to the specified output stream
results in an IOException . |
NullPointerException |
if os is null. |
ClassCastException |
if this Properties object
contains any keys or values that are not
Strings . |
See also:
storeToXML
public void storeToXML (OutputStream os, String comment, String encoding)
Emits an XML document representing all of the properties contained in this table, using the specified encoding.
The XML document will have the following DOCTYPE declaration:
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
If the specified comment is null
then no comment
will be stored in the document.
An implementation is required to support writing of XML documents
that use the "UTF-8
" or "UTF-16
" encoding. An
implementation may support additional encodings.
The specified stream remains open after this method returns.
This method behaves the same as storeToXML(java.io.OutputStream, java.lang.String, java.nio.charset.Charset) except that it will look up the charset using the given encoding name.
Parameters | |
---|---|
os |
OutputStream : the output stream on which to emit the XML document. |
comment |
String : a description of the property list, or null
if no comment is desired. |
encoding |
String : the name of a supported
character encoding |
Throws | |
---|---|
IOException |
if writing to the specified output stream
results in an IOException . |
UnsupportedEncodingException |
if the encoding is not supported by the implementation. |
NullPointerException |
if os is null ,
or if encoding is null . |
ClassCastException |
if this Properties object
contains any keys or values that are not Strings . |
storeToXML
public void storeToXML (OutputStream os, String comment, Charset charset)
Emits an XML document representing all of the properties contained in this table, using the specified encoding.
The XML document will have the following DOCTYPE declaration:
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
If the specified comment is null
then no comment
will be stored in the document.
An implementation is required to support writing of XML documents
that use the "UTF-8
" or "UTF-16
" encoding. An
implementation may support additional encodings.
Unmappable characters for the specified charset will be encoded as numeric character references.
The specified stream remains open after this method returns.
Parameters | |
---|---|
os |
OutputStream : the output stream on which to emit the XML document. |
comment |
String : a description of the property list, or null
if no comment is desired. |
charset |
Charset : the charset |
Throws | |
---|---|
IOException |
if writing to the specified output stream
results in an IOException . |
NullPointerException |
if os or charset is null . |
ClassCastException |
if this Properties object
contains any keys or values that are not Strings . |
stringPropertyNames
public Set<String> stringPropertyNames ()
Returns an unmodifiable set of keys from this property list
where the key and its corresponding value are strings,
including distinct keys in the default property list if a key
of the same name has not already been found from the main
properties list. Properties whose key or value is not
of type String
are omitted.
The returned set is not backed by this Properties
object.
Changes to this Properties
object are not reflected in the
returned set.
Returns | |
---|---|
Set<String> |
an unmodifiable set of keys in this property list where the key and its corresponding value are strings, including the keys in the default property list. |
See also:
toString
public String toString ()
Returns a string representation of this Hashtable
object
in the form of a set of entries, enclosed in braces and separated
by the ASCII characters " ,
" (comma and space). Each
entry is rendered as the key, an equals sign =
, and the
associated element, where the toString
method is used to
convert the key and element to strings.
Returns | |
---|---|
String |
a string representation of this hashtable |
values
public Collection<Object> values ()
Returns a Collection
view of the values contained in this map.
The collection is backed by the map, so changes to the map are
reflected in the collection, and vice-versa. If the map is
modified while an iteration over the collection is in progress
(except through the iterator's own remove
operation),
the results of the iteration are undefined. The collection
supports element removal, which removes the corresponding
mapping from the map, via the Iterator.remove
,
Collection.remove
, removeAll
,
retainAll
and clear
operations. It does not
support the add
or addAll
operations.
Returns | |
---|---|
Collection<Object> |
a collection view of the values contained in this map |
Protected methods
rehash
protected void rehash ()
Increases the capacity of and internally reorganizes this hashtable, in order to accommodate and access its entries more efficiently. This method is called automatically when the number of keys in the hashtable exceeds this hashtable's capacity and load factor.