java.util
Class Properties

java.lang.Object
  java.util.Hashtable
      java.util.Properties

All Implemented Interfaces:

Map

public class Properties
extends Hashtable

A set of persistent properties, which can be saved or loaded from a stream. A property list may also contain defaults, searched if the main list does not contain a property for a given key. An example of a properties file for the german language is given here. This extends the example given in ListResourceBundle. Create a file MyResource_de.properties with the following contents and put it in the CLASSPATH. (The character \u00e4 is the german umlaut)

s1=3
s2=MeineDisk
s3=3. M\u00e4rz 96
s4=Die Diskette ''{1}'' enth\u00e4lt {0} in {2}.
s5=0
s6=keine Dateien
s7=1
s8=eine Datei
s9=2
s10={0,number} Dateien
s11=Das Formatieren schlug fehl mit folgender Exception: {0}
s12=FEHLER
s13=Ergebnis
s14=Dialog
s15=Auswahlkriterium
s16=1,3

Although this is a sub class of a hash table, you should never insert anything other than strings to this property, or several methods, that need string keys and values, will fail. To ensure this, you should use the get/setProperty method instead of get/put. Properties are saved in ISO 8859-1 encoding, using Unicode escapes with a single u for any character which cannot be represented.

See Also:

PropertyResourceBundle

Nested Class Summary

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry

Field Summary

protected Properties

defaults The property list that contains default values for any keys not in this property list.

Constructor Summary

Properties()
Creates a new empty property list with no default values.

Properties(Properties defaults)
Create a new empty property list with the specified default values.

Method Summary

String	getProperty(String key) Gets the property with the specified key in this property list.
void	load(InputStream inStream) Reads a property list from an input stream.
Enumeration	propertyNames() Returns an enumeration of all keys in this property list, including the keys in the default property list.
Object	setProperty(String key, String value) Adds the given key/value pair to this properties.

Methods inherited from class java.util.Hashtable

clear, clone, contains, containsKey, containsValue, elements, entrySet, equals, get, hashCode, isEmpty, keys, keySet, put, putAll, rehash, remove, size, toString, values

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

defaults

protected Properties defaults

The property list that contains default values for any keys not in this property list.

Constructor Detail

Properties

public Properties()

Creates a new empty property list with no default values.

Properties

public Properties(Properties defaults)

Create a new empty property list with the specified default values.

Parameters:

defaults - a Properties object containing the default values

Method Detail

setProperty

public Object setProperty(String key,
                          String value)

Adds the given key/value pair to this properties. This calls the hashtable method put.

Parameters:

key - the key for this property

value - the value for this property

Returns:

The old value for the given key

Since:

1.2

See Also:

getProperty(String)

load

public void load(InputStream inStream)
          throws IOException

Reads a property list from an input stream. The stream should have the following format:
An empty line or a line starting with # or ! is ignored. An backslash (\) at the end of the line makes the line continueing on the next line (but make sure there is no whitespace after the backslash). Otherwise, each line describes a key/value pair.
The chars up to the first whitespace, = or : are the key. You can include this caracters in the key, if you precede them with a backslash (\). The key is followed by optional whitespaces, optionally one = or :, and optionally some more whitespaces. The rest of the line is the resource belonging to the key.
Escape sequences \t, \n, \r, \\, \", \', \!, \#, \ (a space), and unicode characters with the \\uxxxx notation are detected, and converted to the corresponding single character.

# This is a comment
key     = value
k\:5      \ a string starting with space and ending with newline\n
# This is a multiline specification; note that the value contains
# no white space.
weekdays: Sunday,Monday,Tuesday,Wednesday,\\
          Thursday,Friday,Saturday
# The safest way to include a space at the end of a value:
label   = Name:\\u0020

Parameters:

inStream - the input stream

Throws:

IOException - if an error occurred when reading the input

NullPointerException - if in is null

getProperty

public String getProperty(String key)

Gets the property with the specified key in this property list. If the key is not found, the default property list is searched. If the property is not found in the default, null is returned.

Parameters:

key - The key for this property

Returns:

the value for the given key, or null if not found

Throws:

ClassCastException - if this property contains any key or value that isn't a string

See Also:

defaults, setProperty(String, String), #getProperty(String, String)

propertyNames

public Enumeration propertyNames()

Returns an enumeration of all keys in this property list, including the keys in the default property list.

Returns:

an Enumeration of all defined keys