Return to Answer

The explanation for your first two (weird) test numbers is:

Inserting into ArrayList is generally slower because it has to grow once you hit its boundaries. It will have to create a new bigger array, and copy data from the original one.

But when you create an ArrayList that is already huge enough to fit all your inserts (which is your case since you're doing new ArrayList(n+10)) - it will obviously not involve any array copying operations. Adding to it will be even faster than with LinkedList because LinkedList will have to deal with its "links" (pointers), while huge ArrayList just sets value at given (last) index.

Also your tests are not good because each iteration involves autoboxing (conversion from int to Integer) - it will both take additional time to do that and will also screw up the results because of the Integers cache that will get filled on the first pass.

The explanation for your first two (weird) test numbers is:

Inserting into ArrayList is generally slower because it has to grow once you hit its boundaries. It will have to create a new bigger array, and copy data from the original one.

But when you create an ArrayList that is already huge enough to fit all your inserts (which is your case since you're doing new ArrayList(n+10)) - it will obviously not involve any array copying operations. Adding to it will be even faster than with LinkedList because LinkedList will have to deal with its "links" (pointers), while huge ArrayList just sets value at given (last) index.

Also your tests are not good because each iteration involves autoboxing (conversion from int to Integer) - it will both take additional time to do that and will also screw up the results because of the Integers cache that will get filled on the first pass.

The explanation for your first two (weird) test numbers is:

Inserting into ArrayList is generally slower because it has to grow once you hit its boundaries. It will have to create a new bigger array, and copy data from the original one.

But when you create an ArrayList that is already huge enough to fit all your inserts (which is your case since you're doing new ArrayList(n+10)) - it will obviously not involve any array copying operations. Adding to it will be even faster than with LinkedList because LinkedList will have to deal with its "links" (pointers), while huge ArrayList just sets value at given (last) index.

Also your tests are not good because each iteration involves autoboxing (conversion from int to Integer) - it will both take additional time to do that and will also screw up the results because of the Integers autoboxing cache that will get filled on the first pass.

The explanation for your first two (weird) test numbers is:

Inserting into ArrayList is generally slower because it has to grow once you hit its boundaries. It will have to create a new bigger array, and copy data from the original one.

But when you create an ArrayList that is already huge enough to fit all your inserts (which is your case since you're doing new ArrayList(n+10)) - it will obviously not involve any array copying operations. Adding to it will be even faster than with LinkedList because LinkedList will have to deal with its "links" (pointers), while huge ArrayList just sets value at given (last) index.

Also your tests are not good because each iteration involves autoboxing (conversion from int to Integer) - it will both take additional time to do that and will also screw up the results because of the Integers cache that will get filled on the first pass.

The explanation for your first two test numbers is:

Inserting into ArrayList is slower because it has to grow once you hit its boundaries. It will have to create a bigger array, and copy data from the original one.

But when you create an ArrayList that is already huge enough to fit all your inserts (which is your case since you're doing new ArrayList(n+10)) - it will obviously not involve any array copying operations. Adding to it will be even faster than with LinkedList because LinkedList will have to deal with its "links" (pointers), while huge ArrayList just sets value at given (last) index.

Also your tests are not good because each iteration involves autoboxing (conversion from int to Integer) - it will both take additional time to do that and will also screw up the results because of the Integers autoboxing cache that will get filled on the first pass.

The explanation for your first two (weird) test numbers is:

Inserting into ArrayList is generally slower because it has to grow once you hit its boundaries. It will have to create a new bigger array, and copy data from the original one.

But when you create an ArrayList that is already huge enough to fit all your inserts (which is your case since you're doing new ArrayList(n+10)) - it will obviously not involve any array copying operations. Adding to it will be even faster than with LinkedList because LinkedList will have to deal with its "links" (pointers), while huge ArrayList just sets value at given (last) index.

Also your tests are not good because each iteration involves autoboxing (conversion from int to Integer) - it will both take additional time to do that and will also screw up the results because of the Integers autoboxing cache that will get filled on the first pass.