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// ArrayIntList provides an implementation of the IntList interface backed by
// an array. This will provide O(1) performance for methods like get and set
// that access a particular element of the array. The underlying array will be
// doubled in size if necessary to accommodate add operations. The appending
// add has O(1) performance (amortized for doubling when full).
// (GY edited from SR)
public class SimpleArrayIntList extends SimpleAbstractIntList {
private int[] elementData; // list of integers
// elementData.length is the capacity of the array, which is different
// from the number of elements actually being used (size)
private int size; // current number of elements in the list
// Pretty much all your instance variables should be private. We'll
// make a slight exception for this with the ListNode class, where the
// class doesn't have any methods aside from constructors.
// public static final is basically a constant. Everyone can see it, there
// is only one copy per class, and it cannot change once initialized.
// Standard Java convention (people care about this, not the compiler)
// is for all constants to be in all CAPS, with _ separating words.
public static final int DEFAULT_CAPACITY = 100;
// post: constructs an empty list of default capacity
public SimpleArrayIntList() {
// This convenience constructor invokes the master constructor this(int)
this(DEFAULT_CAPACITY);
}
// pre : capacity >= 0
// post: constructs an empty list with the given capacity
// This is the master constructor, with all the possible parameters
// necessary.
public SimpleArrayIntList(int capacity) {
if (capacity < 0)
throw new IllegalArgumentException("negative capacity");
// An array is an object, so we create one with new.
elementData = new int[capacity];
size = 0;
}
// post: returns the current number of elements in the list
// This seemingly pointless simple method is useful because:
// 1) size is now read-only
// 2) we can do accounting, such as logging the number of accesses
// 3) we can have internal units for the computer and external units
// for the user, say in an app using radians inside and degrees outside.
public int size() {
return size;
}
// pre : 0 <= index < size()
// post: returns the integer at the given index in the list
public int get(int index) {
checkIndex(index); // the protected method from the abstract class
return elementData[index];
}
// post: appends the given value to the end of the list
public void add(int value) {
ensureCapacity(size + 1); // if we don't have enough room, get more
elementData[size] = value; // size items means the last
// was at bin (size-1)
size++; // update size because we added an item
}
/////////////////////////////////// We stopped here on Sep 30
///////////////////////////////////////////////////////////////////
// pre: 0 <= index <= size()
// post: inserts the given value at the given index, shifting subsequent
// values right
public void add(int index, int value) {
if (index < 0 || index > size)
throw new IndexOutOfBoundsException("illegal index");
ensureCapacity(size + 1);
for (int i = size; i > index; i--)
elementData[i] = elementData[i - 1];
elementData[index] = value;
size++;
}
// pre : 0 <= index < size()
// post: removes value at the given index, shifting subsequent values left
public void remove(int index) {
checkIndex(index);
for (int i = index; i < size - 1; i++)
elementData[i] = elementData[i + 1];
size--;
}
// pre : 0 <= index < size()
// post: replaces the integer at the given index with the given value
public void set(int index, int value) {
checkIndex(index);
elementData[index] = value;
}
// post: list is empty
public void clear() {
size = 0;
}
// post: ensures that the underlying array has the given capacity; if not,
// the size is doubled (or more if given capacity is even larger)
public void ensureCapacity(int capacity) {
if (capacity > elementData.length) {
int newCapacity = elementData.length * 2 + 1;
if (capacity > newCapacity)
newCapacity = capacity;
int[] newList = new int[newCapacity];
for (int i = 0; i < size; i++)
newList[i] = elementData[i];
elementData = newList;
}
}
}
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