java.util.RandomAccess Maven / Gradle / Ivy

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This work corresponds to the API signatures of JSR 219: Foundation Profile 1.1. In the event of a discrepency between this work and the JSR 219 specification, which is available at http://www.jcp.org/en/jsr/detail?id=219, the latter takes precedence. */ package java.util; /** * Marker interface used by List implementations 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 * performance. * *

It is recognized that the distinction between random and sequential * access is often fuzzy. For example, some List implementations * provide asymptotically linear access times if they get huge, but constant * access times in practice. Such a List implementation * 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);
 * 

 *     for (Iterator i=list.iterator(); i.hasNext(); )
 *         i.next();
 *