In this chapter we introduced the List interface, which extends the Collection interface
by adding several index-based methods. We then studied the ArrayList class, an
implementation of the List interface that allows random access—that is, constanttime
access—of any element from its index. Using an ArrayList object is similar to
using an array, but one important difference is that ArrayList objects are automatically
resizable. When an ArrayList outgrows the current capacity of its underlying
array, an array of 1.5 times that size is created, and the old array is copied to the
larger array. This is similar to what hermit crabs do each time they outgrow their
shell. A further advantage of ArrayList objects over arrays is that, for inserting and
deleting, users are relieved of the burden of writing the code to make space for the
new entry or to close up the space of the deleted entry.
The application of the ArrayList class was in high-precision arithmetic, an essential
component of public-key cryptography.
