What are the new features came in java1.5 ?

In java5 some new features came,
Such as
- Generics
Problem: Collection element types
Cannot be checked at compile time
Assignment must use cast
Can cause runtime errors( ClassCastException)
Solution:
Tell the compiler what type your collection is
Compiler can fill in casts for you
Guaranteed to succeed *
Old code
List l = new LinkedList();
l.add(new Integer(0));
Integer i = (Integer)l.iterator.next();
New code
List l = new LinkedList();
l.add(new Integer(0));
Integer i = l.iterator.next();
- Enhanced for loop (“foreach”)
Problem:
Iterating over collections is tricky
Often, iterator only used to get an element
Iterator is error prone (Occurs three times
in a for loop)
Can produce subtle runtime errors
Solution: Let the compiler do it
New for loop syntax
for (variable : collection)
Old code
void cancelAll(Collection c) {
for (Iterator i = c.iterator(); i.hasNext(); ) {
TimerTask task = (TimerTask)i.next();
task.cancel(); } }
New Code
void cancelAll(Collection c) {
for (TimerTask task : c)
task.cancel();
}
Also works for arrays
- Autoboxing/Unboxing
Problem:
Conversion between primitive types and wrapper objects (and vice-versa)
Needed when adding primitives to a collection
Solution: Let the compiler do it
Integer intObj = 22; // Boxing conversion
int i = (int)intObj // Unboxing conversion
ArrayList al = new ArrayList();
al.add(22); // Boxing conversion
- Type-safe enumerations
Problem:
Variable needs to hold limited set of values
e.g. Card suit can only be Spade, Diamond, Club, Heart
Solution: New type of class declaration
enum type has public, self-typed members for each enum constant new keyword, enum
works with switch statement
- Varargs
Problem:
To have a method that takes a variable number of parameters
Can be done with an array, but not nice
Look at java.text.MessageFormat
Solution: Let the compiler do it for you
New syntax:
public static String format(String fmt,
Object... args);
- Static import
Problem:
Having to fully qualify every static referenced from external classes
Solution: New import syntax
import static TypeName . Identifier ;
import static Typename . * ;
Also works for static methods and enums
e.g Math.sin(x) becomes sin(x)
- Metadata
Problem:
Some APIs require lots of standard code
How to indicate this to a tool
Solution: Annotated source code
e.g.
@remote getPrice(Product p)

Concurrency Utilities
Goal: Beat C performance in high end
server side applications
New framework for locks to provide greater flexibility over synchronized
No more threads, use Executors
Use anExecutor.execute(aRunnable)
Not new Thread(aRunnable).start();
Runnable and Callable
Callable for things that return values and/or exceptions