The Properties Class

Properties is a subclass of Hashtable. It is used to maintain lists of values in which the key is a String and the value is also a String.

The Properties class is used by many other Java classes. For example, it is the type of object returned by System.getProperties( ) when obtaining environmental values.

Properties defines the following instance variable. This variable holds a default property list associated with a Properties object.

Properties defaults;

The Properties defines two constructors. The first version creates a Properties object that has no default values:

Properties( )

The second creates an object that uses propDefault for its default values. In both cases, the property list is empty:

Properties(Properties propDefault)

Apart from the methods defined by Hashtable, Properties defines following methods:

SN	Methods with Description
1	String getProperty(String key) Returns the value associated with key. A null object is returned if key is neither in the list nor in the default property list.
2	String getProperty(String key, String defaultProperty) Returns the value associated with key. defaultProperty is returned if key is neither in the list nor in the default property list.
3	void list(PrintStream streamOut) Sends the property list to the output stream linked to streamOut.
4	void list(PrintWriter streamOut) Sends the property list to the output stream linked to streamOut.
5	void load(InputStream streamIn) throws IOException Inputs a property list from the input stream linked to streamIn.
6	Enumeration propertyNames( ) Returns an enumeration of the keys. This includes those keys found in the default property list, too.
7	Object setProperty(String key, String value) Associates value with key. Returns the previous value associated with key, or returns null if no such association exists.
8	void store(OutputStream streamOut, String description) After writing the string specified by description, the property list is written to the output stream linked to streamOut.