Need of abstract class and Interface.

Abstract class and Interface are used when there is a difference in behavior among the sub-types extending the abstract class or implementing the interface.

Need of abstract class : when the sub-types behavior is partially common and different with respect to the super-type then use an abstract class .
Need of Interface : When the sub-types behavior is totally different then you use an interface.

More clarification let me know :

Avoid Deadlock.

Step to prevent Deadlock :

• to ensure that resources are always acquired in some well-defined order means realeas the lock finally clause.
• synchronized method should never call a synchronized method.

Live Example :

By synchronizing the methods of the kitchen class, we are essentially preventing more than one cook from
using the kitchen at a time; the purpose of having multiple threads is to allow more than one cook to use the
kitchen.

Deadlock Code :

Here you will get clear picture for Deadlock :

http://www.itec.uni-klu.ac.at/~harald/CSE/Content/deadlock.html

Difference between JDK 1.4 and JDK 1.5....?

Sun system added new feature in JDK 1.5 :
1.It's allowed to read Image like BMP and WBMP Image format this feature is not in JDK 1.4.
2.JTable able to support printing functionality that is not available in JDK 1.4.
2. JDK 1.5 support to import static like that import static java.lang.System.out; and we cant write only out.println("India"). This feature is not in JDK 1.4.
3.Generic feature in JDK 1.5 not in JDK 1.4.

For more clarification let me know...