IMPLEMENTING LISTS, STACKS, QUEUES, AND PRIORITY QUEUES - Introduction to Java Programming: Comprehensive Version - page 901

MyAbstractList<E>

MyArrayList<E>

-data: E[]

+MyArrayList()
+MyArrayList(objects: E[])
+trimToSize(): void

Creates a default array list.
Creates an array list from an array of objects.
Trims the capacity of this array list to the list's
current size.
Doubles the current array size if needed.
Throws an exception if the index is out of
bounds in the list.

-ensureCapacity(): void
-checkIndex(index: int): void

F IGURE 24.6

MyArrayList implements a list using an array.

L ISTING 24.3

MyArrayList.java
1 public class MyArrayList<E> extends MyAbstractList<E> {
2 public static final int INITIAL_CAPACITY = 16 ; initial capacity

create an array 3 private E[] data = (E[]) new Object[INITIAL_CAPACITY];

4
5 /** Create a default list */
6 public MyArrayList() {
7 }
8
9 /** Create a list from an array of objects */
10 public MyArrayList(E[] objects) {
11 for ( int i = 0 ; i < objects.length; i++)
12 add(objects[i]); // Warning: don't use super(objects)!
13 }
14
15 @Override /** Add a new element at the specified index */
16 public void add( int index, E e) {
17 ensureCapacity();
18
19 // Move the elements to the right after the specified index
20 for ( int i = size - 1 ; i >= index; i--)
21 data[i + 1 ] = data[i];
22
23 // Insert new element to data[index]
24 data[index] = e;
25
26 // Increase size by 1
27 size++;
28 }
29
30 /** Create a new larger array, double the current size + 1 */
31 private void ensureCapacity() {
32 if (size >= data.length) {
33 E[] newData = (E[])( new Object[size * 2 + 1 ]);
34 System.arraycopy(data, 0 , newData, 0 , size);
35 data = newData;
36 }
37 }
38

no-arg constructor

constructor

add

ensureCapacity

double capacity + 1