Java Language Enhancements
by Benoy Jose
Introduction
The Java language is already powerful enough in many
aspects, but it does not hurt to add a few more
features that would make it more powerful and
programmer friendly. With the advent of Microsoft’s
Microsoft.net, Sun has been under enormous pressure to
enhance the Java language and make it more programmer
friendly. Though the Java community is against major
changes to the language, the
pressure has been on to add few features that were
inherently missing in Java. A major slew of features
like those in Microsoft.net would make Java less
flexible, so Sun has carefully chosen a few features
that already existed in languages like C and C++, but
were left out in the original Java specification.
Keeping this in mind Sun and its partners have
proposed a set of enhancements to the Java language
through the Java specification request JSR 201. The
proposed enhancements are as follows:
- An enhanced "for loop" that would allow easier
iteration over collections.
- An automatic conversion mechanism to convert primitive
types to their corresponding wrappers and vice versa.
- A new syntax for an enumerated type
- A static import.
- Variable-Arity Methods.
These proposed enhancements have been included into the J2SE 1.5
tiger edition which is presently in the beta 1 stage.
Enhanced For Loop:
The "for loop" is a very powerful construct when dealing with
simple loops. But when it comes to a collection of string values
it becomes worse. Take the sample below all the elements of this
ArrayList are Strings yet we need to specify the cast each time
an element is retrieved. Well I am not implying that the
collections framework design is flawed. The idea of collections
to include any object makes it truly object oriented but this
feature brings in an additional burden of checking and
converting objects each time they are stored in a collection.
The enhanced "for loop" makes the iteration through collections
easy while maintaining the integrity of the language.
int [] intArray = new int[10];
for (int i=0; i< 10; i++){
System.out.println (“Value at ”+I + “ is ”+intArray[i]);
}
ArrayList arrayList = (ArrayList) someColl;
for (int i =0; I < arrayList.size(); i++){
String tempString = (String) arrayList.get(i);
}
How about this
for (String tempString : someColl ){
}
In this example tempString is some String where the value is held and
someColl is a collection of type java.util.Collection. The above
piece of code is an example of the new enhanced "for loop"’
proposed by the JSR 201. The enhanced "for loop" makes it easier
to iterate through collections and Arrays while making code
simple and more readable. The enhanced "for" uses the existing
"for" keyword with some modifications so that the virtual
machine is left undisturbed. The enhanced "for" construct is
accommodated by modifying the compiler and these changes do not
affect existing programs in any way. To make this possible a new
interface called the java.lang.Iterable is being introduced. Any
collection that can be used in the enhanced "for loop" needs to be
an instance of the Iterable interface. For the coexistence with
the existing Collections framework the java.langCollection
interface will be retrofitted to implement or extend the
Iterable interface.
The enhanced "for loop" assumes that the elements contained in the
collection are of the same type. If this assertion is false an
improper assignment exception is thrown. Additionally the
enhanced "for loop" acts more like an enhancement to the
"Iterator" interface. The enhanced for loop has some drawbacks
as it does not allow the user to modify or delete elements in a
collection as an iteration is being done. This is more on the
lines of what the java.util.Iterator does, the enhanced "for loop"
actually moves through the collection and exhausts it as it
finishes through it, but this does not mean that the collection
is exhausted or deleted, the rules that apply for the Iterator
apply for the enhanced "for loop". The enhanced "for" also does
not allow simultaneous iterations over multiple collections. A
sample of a HashMap is given below:
HaspMap myMap = someHashMap;
for (Map.Entry<String, String> e : myMap.entrySet()){
System.out.println ("Key "+ e.getKey() + " Value "+ e.getValue());
}
New on the Java Boutique:
New Review:
Time Management Made Easy with the Quartz Enterprise Job Scheduler
Why not just use the Java timer API? This open source scheduling
API boasts simplicity, ease-of-integration, a well-rounded feature
set, and it's free!
New Applet:
Reverse Complement
Reverse Complement is a simple applet that converts DNA or RNA
sequences into three useful formats.
Elsewhere on internet.com:
WebDeveloper Java
Lots of Java information on webdeveloper.com
WDVL Java
Thorough Java resource at the Web Developer's Virtual Library.
ScriptSearch Java
Hundreds of free Java code files to download.
jGuru: Your View of the Java Universe
Customizable portal with online training, FAQs, regular news updates, and tutorials.
| 
