Generics and the ArrayList Class - Java - page 707

Self-Test Exercises
1. Suppose list is an object of the class ArrayList<String> . How do you add the string
"Hello" to the ArrayList list ?
2. Suppose instruction is an object of the class ArrayList<String> that contains
the string "Stop" at index position 5 . How do you change the string at index posi-
tion 5 to "Go" (without changing any of the elements at other positions)?
3. Suppose instruction is an object of the class ArrayList<String> that contains
strings at index positions 0 through 10 . How do you insert the string "Go" at
index position 5 so that no strings are removed from the list instruction ?
4. Can you use the method set to place an element in an ArrayList at any index
you want?
5. Can you use the two-argument version of the method add to add an element in an
ArrayList at any index you want?
6. Consider the following two method invocations. Are there values of index1
that are allowed but that are not allowed for index2 ? Are there values of index2
that are allowed but that are not allowed for index1 ? list is an object of the class
Array-List<String >.
list.set(index1, "Hello");
list.add(index2, "Hello");
7. If you create an ArrayList with the following statement, can the ArrayList con-
tain more than 20 elements?
ArrayList<Double> myList = new ArrayList<Double>(20);
Methods in the Class ArrayList
With arrays, the square brackets and the instance variable length are the only tools
automatically provided for you, the programmer. If you want to use arrays for other
things, you must write code to manipulate the arrays. ArrayList s, on the other hand,
come with a selection of powerful methods that can do many of the things for which
you would need to write code in order to do with arrays. For example, the class Array-
List has a version of the method add that inserts a new element between two elements
in the ArrayList . Most of these methods are described in Display 14.1.
Display 14.1 Some Methods in the Class ArrayList (part 1 of 4)
CONSTRUCTORS
public ArrayList< Base_Type >( int initialCapacity)
Creates an empty ArrayList with the specified Base_Type and initial capacity.
(continued)