Java Notes-11

summary:synchronized and unsynchronized collections, Properties
-in Many applications, there is no need for synchronization, so the collections API doesnot provide it by default. Instead, you can create a synchronized version of any collection

Using the following methods of the collections class:

public static Collection synchronizedcollection (Collection c) public static Set Synchronizedset (Set s) public static List s Ynchronizedlist (list list) public static Map Synchronizedmap (map m) public static SortedSet Synchronizedsortedset ( SortedSet s) public static SortedMap Synchronizedsortedmap (SortedMap m)

-for example, the following shows how to create a threadsafe List

List List = new ArrayList (); List synclist = collections.synchronizedlist (list);

-this is important, so remember this! Although synchronized collections is Threadsafe, the Iterator s returned from them is not.

Synchronized (synclist) {Iterator Iterator = Synclist.iterator ();//do stuff with the Iterator here}

-the Java.util.concurrent.ConcurrentHashMap class is part of the Concurrency Utilities package and provides a Map that P Erforms well under multithreaded access.

-you can use the collections class to create read-only versions of any collection

public static Collection unmodifiablecollection (Collection c) public static Set Unmodifiableset (Set s) public static List U Nmodifiablelist (list list) public static Map Unmodifiablemap (map m) public static SortedSet Unmodifiablesortedset ( SortedSet s) public static SortedMap Unmodifiablesortedmap (SortedMap m)

-the Java.util.Properties class is a specialized hash table for strings. Properties is generally used to hold textual configuration data.

-any string values can stored as key/value pairs in a Properties table. However, the Convention is-use-a dot-separated naming hierarchy to-group property names into
Logical structures.

Properties Props = new properties ();p rops.setproperty ("Myapp.xsize", "");p rops.setproperty ("Myapp.ysize", "79");

String xsize = Props.getproperty ("Myapp.xsize");

You can save a Properties table to an outputstream using the Save () method. The property information was output in a flat ASCII format.

Props.save (System.out, "Application Parameters");

-the load () method reads the previously saved contents of a Properties object from an InputStream

FileInputStream fin, ..... Properties Props = new properties () Props.load (Fin);

-the Properties class also contains Storetoxml () and LoadFromXML () methods. These operate just like the Save () and load () methods but write a XML file like the following

<?xml version= "1.0" encoding= "UTF-8"? ><! DOCTYPE Properties SYSTEM "Http://java.sun.com/dtd/properties.dtd" ><properties><comment>my Properties</comment><entry key= "myapp.ysize" >79</entry><entry key= "MyApp.xsize" >52</ Entry></properties>

-the Java.lang.System class provides access to basic System environment information through the static System.getpropert IES () method. This method returns a properties table, contains system Properties.

Next:the Preference API

Java Notes-11