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refactor: DynamicArray (#5346)

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This commit is contained in:
Alex Klymenko
2024-08-19 10:15:47 +02:00
committed by GitHub
parent 33fd79ad55
commit 04eae87512
2 changed files with 339 additions and 107 deletions
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191
src/main/java/com/thealgorithms/datastructures/dynamicarray/DynamicArray.java
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@ -10,145 +10,143 @@ import java.util.stream.Stream;
import java.util.stream.StreamSupport;
/**
* This class implements a dynamic array
* This class implements a dynamic array.
*
* @param <E> the type that each index of the array will hold
*/
public class DynamicArray<E> implements Iterable<E> {
private static final int DEFAULT_CAPACITY = 16;
private int capacity;
private int size;
private int modCount; // Tracks structural modifications for the iterator
private Object[] elements;
/**
* constructor
* Constructor with initial capacity.
*
* @param capacity the starting length of the desired array
* @throws IllegalArgumentException if the specified capacity is negative
*/
public DynamicArray(final int capacity) {
if (capacity < 0) {
throw new IllegalArgumentException("Capacity cannot be negative.");
}
this.size = 0;
this.capacity = capacity;
this.elements = new Object[this.capacity];
this.modCount = 0;
this.elements = new Object[capacity];
}
/**
* No-args constructor
* No-args constructor with default capacity.
*/
public DynamicArray() {
this(DEFAULT_CAPACITY);
}
/**
* Adds an element to the array If full, creates a copy array twice the size
* of the current one
* Adds an element to the array. If full, creates a new array with double the size.
*
* @param element the element of type <E> to be added to the array
* @param element the element to be added to the array
*/
public void add(final E element) {
if (this.size == this.elements.length) {
this.elements = Arrays.copyOf(this.elements, newCapacity(2 * this.capacity));
}
this.elements[this.size] = element;
size++;
ensureCapacity(size + 1);
elements[size++] = element;
modCount++; // Increment modification count
}
/**
* Places element of type <E> at the desired index
* Places an element at the desired index, expanding capacity if necessary.
*
* @param index the index for the element to be placed
* @param index the index for the element to be placed
* @param element the element to be inserted
* @throws IndexOutOfBoundsException if n is less than 0 or greater or equal to the number of elements in the array
*/
public void put(final int index, E element) {
this.elements[index] = element;
if (index < 0) {
throw new IndexOutOfBoundsException("Index cannot be negative.");
}
ensureCapacity(index + 1);
elements[index] = element;
if (index >= size) {
size = index + 1;
}
modCount++; // Increment modification count
}
/**
* get method for element at a given index returns null if the index is
* empty
* Gets the element at a given index.
*
* @param index the desired index of the element
* @return <E> the element at the specified index
* @return the element at the specified index
* @throws IndexOutOfBoundsException if n is less than 0 or greater or equal to the number of elements in the array
*/
@SuppressWarnings("unchecked")
public E get(final int index) {
return getElement(index);
if (index < 0 || index >= size) {
throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
}
return (E) elements[index];
}
/**
* Removes an element from the array
* Removes an element from the array.
*
* @param index the index of the element to be removed
* @return <E> the element removed
* @return the element removed
* @throws IndexOutOfBoundsException if n is less than 0 or greater or equal to the number of elements in the array
*/
public E remove(final int index) {
final E oldElement = getElement(index);
fastRemove(this.elements, index);
if (this.capacity > DEFAULT_CAPACITY && size * 4 <= this.capacity) {
this.elements = Arrays.copyOf(this.elements, newCapacity(this.capacity / 2));
if (index < 0 || index >= size) {
throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
}
@SuppressWarnings("unchecked") E oldElement = (E) elements[index];
fastRemove(index);
modCount++; // Increment modification count
return oldElement;
}
/**
* get method for size field
* Gets the size of the array.
*
* @return int size
* @return the size
*/
public int getSize() {
return this.size;
return size;
}
/**
* isEmpty helper method
* Checks if the array is empty.
*
* @return boolean true if the array contains no elements, false otherwise
* @return true if the array contains no elements, false otherwise
*/
public boolean isEmpty() {
return this.size == 0;
return size == 0;
}
public Stream<E> stream() {
return StreamSupport.stream(spliterator(), false);
}
private void fastRemove(final Object[] elements, final int index) {
final int newSize = this.size - 1;
if (newSize > index) {
System.arraycopy(elements, index + 1, elements, index, newSize - index);
private void ensureCapacity(int minCapacity) {
if (minCapacity > elements.length) {
int newCapacity = Math.max(elements.length * 2, minCapacity);
elements = Arrays.copyOf(elements, newCapacity);
}
this.size = newSize;
this.elements[this.size] = null;
}
private E getElement(final int index) {
return (E) this.elements[index];
private void fastRemove(int index) {
int numMoved = size - index - 1;
if (numMoved > 0) {
System.arraycopy(elements, index + 1, elements, index, numMoved);
}
elements[--size] = null; // Clear to let GC do its work
}
private int newCapacity(int capacity) {
this.capacity = capacity;
return this.capacity;
}
/**
* returns a String representation of this object
*
* @return String a String representing the array
*/
@Override
public String toString() {
return Arrays.toString(Arrays.stream(this.elements).filter(Objects::nonNull).toArray());
return Arrays.toString(Arrays.copyOf(elements, size));
}
/**
* Creates and returns a new Dynamic Array Iterator
*
* @return Iterator a Dynamic Array Iterator
*/
@Override
public Iterator<E> iterator() {
return new DynamicArrayIterator();
@ -157,71 +155,50 @@ public class DynamicArray<E> implements Iterable<E> {
private final class DynamicArrayIterator implements Iterator<E> {
private int cursor;
private int expectedModCount;
@Override
public boolean hasNext() {
return this.cursor != size;
DynamicArrayIterator() {
this.expectedModCount = modCount;
}
@Override
public boolean hasNext() {
checkForComodification();
return cursor < size;
}
@Override
@SuppressWarnings("unchecked")
public E next() {
if (this.cursor > DynamicArray.this.size) {
checkForComodification();
if (cursor >= size) {
throw new NoSuchElementException();
}
if (this.cursor > DynamicArray.this.elements.length) {
throw new ConcurrentModificationException();
}
final E element = DynamicArray.this.getElement(this.cursor);
this.cursor++;
return element;
return (E) elements[cursor++];
}
@Override
public void remove() {
if (this.cursor < 0) {
if (cursor <= 0) {
throw new IllegalStateException();
}
checkForComodification();
DynamicArray.this.remove(--cursor);
expectedModCount = ++modCount;
}
DynamicArray.this.remove(this.cursor);
this.cursor--;
private void checkForComodification() {
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
}
@Override
public void forEachRemaining(Consumer<? super E> action) {
Objects.requireNonNull(action);
for (int i = 0; i < DynamicArray.this.size; i++) {
action.accept(DynamicArray.this.getElement(i));
while (hasNext()) {
action.accept(next());
}
}
}
/**
* This class is the driver for the DynamicArray<E> class it tests a variety
* of methods and prints the output
*/
public static void main(String[] args) {
DynamicArray<String> names = new DynamicArray<>();
names.add("Peubes");
names.add("Marley");
for (String name : names) {
System.out.println(name);
}
names.stream().forEach(System.out::println);
System.out.println(names);
System.out.println(names.getSize());
names.remove(0);
for (String name : names) {
System.out.println(name);
}
}
}