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FlexDoc/Javadoc 2.0 Demo Java Doc |
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(InputStream) and storeToXML(OutputStream, String, 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">Note that the system URI (http://java.sun.com/dtd/properties.dtd) is not accessed when exporting or importing properties; it merely serves as a string to uniquely identify the DTD, which is:
<?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.
Nested Class Summary |
Nested classes/interfaces inherited from interface java.util.Map |
Field Summary |
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protected Properties |
A property list that contains default values for any keys not
found in this property list.
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Constructor Summary |
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Creates an empty property list with no default values.
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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.
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Properties(Properties defaults)
Creates an empty property list with the specified defaults.
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Method Summary |
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void |
clear()
Clears this hashtable so that it contains no keys.
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clone()
Creates a shallow copy of this hashtable.
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Attempts to compute a mapping for the specified key and its current
mapped value (or null if there is no current mapping).
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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.
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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.
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boolean |
Tests if some key maps into the specified value in this hashtable.
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boolean |
containsKey(Object key)
Tests if the specified object is a key in this hashtable.
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boolean |
containsValue(Object value)
Returns true if this hashtable maps one or more keys to this value.
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elements()
Returns an enumeration of the values in this hashtable.
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entrySet()
Returns a Set view of the mappings contained in this map.
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boolean |
Compares the specified Object with this Map for equality,
as per the definition in the Map interface.
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void |
Performs the given action for each entry in this map until all entries
have been processed or the action throws an exception.
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Returns the value to which the specified key is mapped,
or null if this map contains no mapping for the key.
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Returns the value to which the specified key is mapped, or
defaultValue if this map contains no mapping for the key.
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getProperty(String key)
Searches for the property with the specified key in this property list.
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Searches for the property with the specified key in this property list.
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int |
hashCode()
Returns the hash code value for this Map as per the definition in the
Map interface.
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boolean |
isEmpty()
Tests if this hashtable maps no keys to values.
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keys()
Returns an enumeration of the keys in this hashtable.
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keySet()
Returns a Set view of the keys contained in this map.
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void |
list(PrintStream out)
Prints this property list out to the specified output stream.
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void |
list(PrintWriter out)
Prints this property list out to the specified output stream.
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void |
load(InputStream inStream)
Reads a property list (key and element pairs) from the input
byte stream.
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void |
Reads a property list (key and element pairs) from the input
character stream in a simple line-oriented format.
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void |
Loads all of the properties represented by the XML document on the
specified input stream into this properties table.
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If the specified key is not already associated with a value or is
associated with null, associates it with the given non-null value.
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Enumeration<?> |
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.
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Maps the specified key to the specified
value in this hashtable.
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void |
Copies all of the mappings from the specified map to this hashtable.
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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.
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protected void |
rehash()
Increases the capacity of and internally reorganizes this
hashtable, in order to accommodate and access its entries more
efficiently.
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Removes the key (and its corresponding value) from this
hashtable.
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boolean |
Removes the entry for the specified key only if it is currently
mapped to the specified value.
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Replaces the entry for the specified key only if it is
currently mapped to some value.
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boolean |
Replaces the entry for the specified key only if currently
mapped to the specified value.
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void |
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.
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void |
Deprecated. This method does not throw an IOException if an I/O error
occurs while saving the property list.
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Calls the Hashtable method put.
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int |
size()
Returns the number of keys in this hashtable.
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void |
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.
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void |
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.
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void |
Emits an XML document representing all of the properties contained
in this table.
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void |
Emits an XML document representing all of the properties contained
in this table, using the specified encoding.
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void |
Emits an XML document representing all of the properties contained
in this table, using the specified encoding.
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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.
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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). |
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values()
Returns a Collection view of the values contained in this map.
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Methods inherited from class java.lang.Object |
Methods inherited from interface java.util.Map |
public Properties |
() |
public Properties |
(int initialCapacity) |
public Properties |
(Properties defaults) |
public Object setProperty |
public void load |
(Reader reader) |
throws |
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 :BeautyAs another example, the following three lines specify a single property:
fruits apple, banana, pear, \ cantaloupe, watermelon, \ kiwi, mangoThe key is "fruits" and the associated element is:
"apple, banana, pear, cantaloupe, watermelon, kiwi, mango"Note that a space appears before each \ 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:
cheesesspecifies that the key is "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:
The specified stream remains open after this method returns.
public void load |
(InputStream inStream) |
throws |
The specified stream remains open after this method returns.
public void save |
public void store |
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throws |
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.
public void store |
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throws |
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:
After the entries have been written, the output stream is flushed. The output stream remains open after this method returns.
public void loadFromXML |
(InputStream in) |
throws |
The XML document must have the following DOCTYPE declaration:
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">Furthermore, the document must satisfy the properties DTD described above.
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.
public void storeToXML |
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throws |
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");.
public void storeToXML |
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throws |
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(OutputStream os, String comment, Charset charset) except that it will look up the charset using the given encoding name.
public void storeToXML |
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throws |
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.
public String getProperty |
(String key) |
public String getProperty |
public Enumeration<?> propertyNames |
() |
() |
The returned set is not backed by this Properties object. Changes to this Properties object are not reflected in the returned set.
public void list |
(PrintStream out) |
public void list |
(PrintWriter out) |
public int size |
() |
public boolean isEmpty |
() |
() |
() |
public boolean contains |
(Object value) |
Note that this method is identical in functionality to containsValue, (which is part of the Map interface in the collections framework).
public boolean containsValue |
(Object value) |
Note that this method is identical in functionality to contains (which predates the Map interface).
public boolean containsKey |
(Object key) |
public Object get |
(Object 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.)
public Object put |
The value can be retrieved by calling the get method with a key that is equal to the original key.
public Object remove |
(Object key) |
public void putAll |
(Map<?,?> t) |
public void clear |
() |
public String toString |
() |
,
" (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.() |
() |
() |
public boolean equals |
(Object o) |
public int hashCode |
() |
public Object getOrDefault |
public void forEach |
public void replaceAll |
public Object putIfAbsent |
public boolean remove |
public boolean replace |
public Object replace |
public Object computeIfAbsent |
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.
public Object computeIfPresent |
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.
public Object compute |
map.compute(key, (k, v) -> (v == null) ? msg : v.concat(msg))
(Method 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.
public Object merge |
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.
protected void rehash |
() |
public Object clone |
() |
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FlexDoc/Javadoc 2.0 Demo Java Doc |