public interface RandomAccess
Listimplementations to indicate that they support fast (generally constant time) random access. The primary purpose of this interface is to allow generic algorithms to alter their behavior to provide good performance when applied to either random or sequential access lists.
The best algorithms for manipulating random access lists (such as
ArrayList) can produce quadratic behavior when applied to
sequential access lists (such as
LinkedList). Generic list
algorithms are encouraged to check whether the given list is an
instanceof this interface before applying an algorithm that would
provide poor performance if it were applied to a sequential access list,
and to alter their behavior if necessary to guarantee acceptable
It is recognized that the distinction between random and sequential
access is often fuzzy. For example, some
provide asymptotically linear access times if they get huge, but constant
access times in practice. Such a
should generally implement this interface. As a rule of thumb, a
List implementation should implement this interface if,
for typical instances of the class, this loop:
for (int i=0, n=list.size(); i < n; i++) list.get(i);runs faster than this loop:
for (Iterator i=list.iterator(); i.hasNext(); ) i.next();
This interface is a member of the Java Collections Framework.
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