CS1110 Lab 05. Class Vector Spring 2009
Name ___________________ Netid_____________________
Class java.util.Vector provides the ability to maintain a growable/shrinkable list of objects, which can
be of great utility in cases where you don't know ahead of time how many objects will be in the final list.
In this lab, you will gain some experience with class Vector and learn just how useful it can be. This
material is covered in Sec. 5.3 (pp. 184-- 188) of the text. After the lab, study that section. Also, the API is
your friend. Use it! Clicking this link will open the API spec of class Vector in a new window.
A History Lesson
The developers of Java knew early on that they wanted some kind of growable list, so they created class
Vector and shipped it out with Java v1.0. Later, however, they wanted to generalize the idea of a list. So
they created new classes that provide a more general implementation than Vector. Rather than get rid of
Vector —for "backward compatability" reasons, you can't simply throw out old stuff— for Java v1.2 the
developers added new methods to class Vector so that it would be consistent with the other, newer,
classes. Many of these new methods do the same thing as the old ones. Some of the old ones are
"deprecated" (to deprecate means to disapprove of, but often only mildly so). But they will NOT go away,
and you can use them. There is also a new class ArrayList, which can be used in place of Vector.
Caution: Another important history lesson
Several years ago, Java switched from version 1.4 of the language to version 1.5. Java 1.5 and 1.6 make it
easier to work with Vectors of a particular class of elements, like a Vector of elements of class
Character, which we will be working with here. If your computer has Java 1.4, you have two options:
1. Deinstall the Java 1.4 compiler and install Java 1.5 or 1.6.
2. For this lab, follow the instructions in the comment that appears at the top of file Lab05.java, which
you will obtain later from the course web page.
What a Vector contains:
A Vector v contains a list of elements, numbered 0, 1, 2, .... Function v.size() tells how many elements
are in the list. We use the following non-Java notation to refer to parts of the list. The notation helps us
write things more clearly and succinctly. We refer to the elements in the list as v[0], v[1], ...,
v[v.size()–1]. We refer to part of the list, say elements v[h], v[h+1], ..., v[k], using v[h..k]. We also
write v[h..] to mean v[h],v[h+1],...,v[v.size()-1].
In Java 1.5, use this assignment statement to create a Vector that can contain elements only of class C and
store its name in v:
Vector <C> v= new Vector <C>();
The appearance of <C> says that the Vector may contain only elements of class C. In this lab, we will be
working with Vector<Character>, meaning a Vector whose elements are of class Character.
Vector v has a capacity, which is the number of elements for which space in the computer memory has
been allocated. This is different from its size, which is the number of elements in it. When an element is to
be added to v but the size is already equal to the capacity, Java allocates space for more elements —for
reasons of efficiency, the capacity is usually doubled. The capacity can also be controlled by the
programmer.
Here is a list of the old methods, the corresponding new ones, and what they do:
Old method New method Purpose
