Data structures usefull links

http://www.careerride.com/Data-Structure-Interview-Questions.aspx

http://www.dsalgo.com/

http://uniqueminds.in/Thread-Data-Structures-and-Algorithm-Interview-Questions-for-Java-Programmers

http://www.idevelopment.info/data/Programming/data_structures/overview/Data_Structures_Algorithms_Introduction.shtml

http://www.javaworld.com/article/2073390/core-java/datastructures-and-algorithms--part-1.html

how to know the constraints on table in oracle..............

select * from user_cons_columns ucc, user_constraints uc 

where uc.constraint_name=ucc.constraint_name

and uc.constraint_type='P' and uc.table_name = 'Table Name';

R = Referential Constraint/Foreign Key constraint

C = Check Constraint

P = Primary Key

U = Unique Key

(or)

select 

   cons.owner            as child_owner, 

   cons.table_name       as child_table,

   cons.constraint_name     constaint_name,

   cons.constraint_type     constraint_type,

   col.owner                parent_owner, 

   col.table_name           parent_table,

   col.column_name          column_name

from dba_cons_columns      col, 

     dba_constraints       cons

where 

   cons.r_owner = col.owner

and 

   cons.r_constraint_name = col.constraint_name

and 

   cons.table_name = 'Table Name';

   

(or)

   select * 

from

    all_constraints 

where

    r_constraint_name in

    (select       constraint_name

    from

       all_constraints

    where

       table_name='Table Name') 

Debugging techniques in Eclipse............

http://eclipsesource.com/blogs/2013/01/08/effective-java-debugging-with-eclipse/
http://www.vogella.com/articles/EclipseDebugging/article.html

Java API- Implementations

Please refer the below site for the java open source  API & its implementations.
http://java-source.net/
http://freecode.com/tags/java-libraries
http://www.jdocs.com/page/AllLibraries
http://www.theserverside.com/