java - mystery about Linked_List traversing -

the answer might obvious, still feel need ask. programmed simple linked_list fun , training , noticed 1 method supposed print elements of list runs faster method prints list backward.

i kept thinking reason explain this, kept going in circle, interesting know why.

here first method (this simple traversing of list)

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public void list(){     node<e> iter = head;         while(iter != null){             system.out.print(iter.getvalue() + ", ");             iter = iter.getnext();         } } 

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here other method, prints list backward

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public void list_inverse(){     node<e> iter = head;     stack<node<e>> stack = new stack<node<e>>();         while(iter != null){             stack.push(iter);             iter = iter.getnext();         }         while(!stack.isempty()){             node<e> tmp = stack.peek();             stack.pop();             system.out.print(tmp.getvalue() + ", ");         } } 

so idea of second method go through list , add each item stack. after reaching end, print element contained in stack. can see, second method supposed run in longer period of time.

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in main method have :

    long starttime = system.nanotime();     list.list();     long elapsedtime = system.nanotime();     system.out.println();     long starttime2 = system.nanotime();     list.list_inverse();     long elapsedtime2 = system.nanotime(); 

the output had :

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give number list, if want stop, write stop 1 2 3 4 5 6 7 8 9 10 stop  1, 2, 3, 4, 5, 6, 7, 8, 9, 10, //first method 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, // second method  has taken 8.15e-5 second list , 5.19e-5 second list_inverse 

stack in java uses vector internally. vector uses array, stores elements in consecutive memory locations. hence, jvm doesn't need go memory location pointed reference retrieve values. can scan next memory location , values.

i believe main reason difference in execution times first , second method. pure guesswork though ;-)