Lists - Data Structures and Abstractions with Java - page 313

Two of the constructors available for ArrayList are as follows:
public ArrayList()
Creates an empty list with an initial capacity of 10. The list increases its capacity as needed by
an unspecified amount.
public ArrayList( int initialCapacity)
Creates an empty list with the specified initial capacity. The list increases its capacity as
needed by an unspecified amount.

12.14

The class java.util.Vector , which we described in Chapter 6, is similar to ArrayList . Both classes
implement the same interfaces: java.util.List , as well as others. Even so, Vector contains a few
more methods than ArrayList . We will ignore these extra methods, as they mostly are redundant.
You can use either ArrayList or Vector as an implementation of the interface List . For exam-
ple, you could write the following statement to define a list of strings:
List<String> myList = new ArrayList<String>();
Now myList has only the methods declared in the interface List .
Our ListInterface is somewhat simpler than Java's List . It has fewer methods, and they do
not throw an exception when given an illegal position. We can retain the simplicity of our interface
and still make use of an existing class by using either ArrayList or Vector in an implementation of
ListInterface . We will show you how in the next chapter. Although we will use Vector , you
could use ArrayList just as easily.

C HAPTER S UMMARY

•

A list is an object whose data consists of ordered entries. Each entry is identified by its position within the list.

• The ADT list specifies operations that add an entry either to the end of a list or at a given position within the

list. Among its other operations are those that retrieve, remove, or replace the entry at a given position.

• A client manipulates or accesses a list's entries by using only the operations defined for the ADT list.

•

The entries in a bag are unordered, whereas the entries in a list, a stack, a queue, a deque, or a priority queue
do have an order. A list, unlike these other collections, enables you to add, retrieve, remove, or replace an
entry at any given position.

E XERCISES

1.

If myList is an empty list of strings, what does it contain after the following statements execute?
myList.add("A");
myList.add("B");
myList.add("C");
myList.add("D");
myList.add(1, "one");
myList.add(1, "two");
myList.add(1, "three");
myList.add(1, "four");

2.

If myList is an empty list of strings, what does it contain after the following statements execute?
myList.add("alpha");
myList.add(1, "beta");
myList.add("gamma");
myList.add(2, "delta");
myList.add(4, "alpha");
myList.remove(2);
myList.remove(2);
myList.replace(3, "delta");