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 define the following instance variable. This variable holds a default property list associated with a Properties object.
Apart from the methods defined by Hashtable, Properties define the following methods −
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 define the following instance variable. This variable holds a default property list associated with a Properties object.
Properties defaults;Following is the list of constructors provided by the properties class.
Sr.No. | Constructor & Description |
---|---|
1 | Properties( ) This constructor creates a Properties object that has no default values. |
2 | Properties(Properties propDefault) Creates an object that uses propDefault for its default values. In both cases, the property list is empty. |
Sr.No. | Method & Description |
---|---|
1 | String getProperty(String key) Returns the value associated with the key. A null object is returned if the key is neither in the list nor in the default property list. |
2 | String getProperty(String key, String defaultProperty) Returns the value associated with the key; defaultProperty is returned if the 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 the key. Returns the previous value associated with the 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. |
Example
The following program illustrates several of the methods supported by this data structure −import java.util.*; public class PropDemo { public static void main(String args[]) { Properties capitals = new Properties(); Set states; String str; capitals.put("Illinois", "Springfield"); capitals.put("Missouri", "Jefferson City"); capitals.put("Washington", "Olympia"); capitals.put("California", "Sacramento"); capitals.put("Indiana", "Indianapolis"); // Show all states and capitals in hashtable. states = capitals.keySet(); // get set-view of keys Iterator itr = states.iterator(); while(itr.hasNext()) { str = (String) itr.next(); System.out.println("The capital of " + str + " is " + capitals.getProperty(str) + "."); } System.out.println(); // look for state not in list -- specify default str = capitals.getProperty("Florida", "Not Found"); System.out.println("The capital of Florida is " + str + "."); } }
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