CS1110 Lab 05. Class Vector Fall 2008
Name ___________________ Netid_____________________
Class java.util.Vector provides the ability to maintain a growable/shrinkable list of objects. 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! For this lab, you can go
directly to the Vector page of the API. Clicking the link will open the page 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"(deprecate means to disapprove of, often with mildness). But they will NOT go away, and you
can use them.
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 Java 1.6
makes 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]. If we want to refer to part of the list, say elements v[h], v[h+1], ..., v[k], we write v[h..k].
In Java 1.5, you create a Vector that can contain elements only of a class C and store its name in a variable
using this assignment and new expression:
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 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.
