Collections Framework Change Summary - JDK 5 Documentation v1.2.2, Java 2 SDK 英文文档

Collections Framework API Change Summary

We received hundreds of excellent suggestions concerning previous releases of the collections framework. Suggestions came from companies, universities, and individuals all around the world. We're truly thankful for these suggestions, and we've incorporated many of them. This page summarizes the differences between the Beta4 and FCS releases, along with a brief rationale for each change.

Their are very few changes in this release, only one of which has the potential to cause compatibity problems (the change to ListIterator.add semantics).

ListIterator Interface

Modified add semantics. Previously, the newly added element was inserted after the cursor; now it's inserted before the cursor. In general, people do not want to see the element they added as the iteration continues, so they were forced to follow every call to ListIterator.add with an (extra) call to ListIterator.next. Worse, repeated calls to ListIterator.add caused the new elements to stack up backwards unless the caller threw in a call to next after each call to add. These calls to next after each insert are no longer necessary. In effect they're now done automatically.

AbstractList Implementation

Added protected removeRange method, and modified the clear method to rely on the new method. Overriding this method can significantly improve the performance of list.subList(i, j).clear(). In the case of ArrayList and Vector, the performance used to be quadratic, and now it's linear with a very small constant factor. The good performance applies to subLists of subLists (ad infinitum) as well.

Array Operations

Added range versions of the sort calls. These calls are useful in conjunction with array-based data structures where only a parts of the array is "active" at any given time.

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