printing from head 
Current: 0	Previous: 	Next: 30
Current: 30	Previous: 0	Next: line1
Current: line1	Previous: 0	Next: line2
Current: line2	Previous: line1	Next: line3
Current: line3	Previous: line2	Next: line4
Current: line4	Previous: line3	Next: line5


Printing From tail 
Current: line5	Previous: 40	Next: 
Current: 40	Previous: line4	Next: line5
Current: line4	Previous: line3	Next: line5
Current: line3	Previous: line2	Next: line4
Current: line2	Previous: line1	Next: line3
Current: line1	Previous: 0	Next: line2
Current: 0	Previous: 	Next: 30