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package DataStructures.DynamicArray;

import java.util.*;

import java.util.function.Consumer;

import java.util.stream.Stream;

import java.util.stream.StreamSupport;

/**

* 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 int capacity;

private int size;

private Object[] elements;

/**

* constructor

*

* @param capacity the starting length of the desired array

*/

public DynamicArray(final int capacity) {

this.size = 0;

this.capacity = capacity;

this.elements = new Object[this.capacity];

}

/** No-args constructor */

public DynamicArray() {

this.size = 0;

this.capacity = 10;

this.elements = new Object[this.capacity];

}

/**

* Doubles the capacity of the array

*

* @return int the new capacity of the array

*/

public int newCapacity() {

this.capacity *= 2;

// changed from this.capacity <<= 1; now much easier to understand

return this.capacity;

}

/**

* Adds an element to the array If full, creates a copy array twice the size of the current one

*

* @param element the element of type <E> 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());

}

this.elements[this.size] = element;

size++;

}

/**

* Places element of type <E> at the desired index

*

* @param index the index for the element to be placed

* @param element the element to be inserted

*/

public void put(final int index, E element) {

this.elements[index] = element;

}

/**

* get method for element at a given index returns null if the index is empty

*

* @param index the desired index of the element

* @return <E> the element at the specified index

*/

public E get(final int index) {

return getElement(index);

}

/**

* Removes an element from the array

*

* @param index the index of the element to be removed

* @return <E> the element removed

*/

public E remove(final int index) {

final E oldElement = getElement(index);

fastRemove(this.elements, index);

return oldElement;

}

/**

* get method for size field

*

* @return int size

*/

public int getSize() {

return this.size;

}

/**

* isEmpty helper method

*

* @return boolean true if the array contains no elements, false otherwise

*/

public boolean isEmpty() {

return this.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);

}

elements[this.size = newSize] = null;

}

private E getElement(final int index) {

return (E) this.elements[index];

}

/**

* 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());

}

/**

* Creates and returns a new Dynamic Array Iterator

*

* @return Iterator a Dynamic Array Iterator

*/

@Override

public Iterator iterator() {

return new DynamicArrayIterator();

}

private class DynamicArrayIterator implements Iterator<E> {

private int cursor;

@Override

public boolean hasNext() {

return this.cursor != size;

}

@Override

public E next() {

if (this.cursor > DynamicArray.this.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;

}

@Override

public void remove() {

if (this.cursor < 0) throw new IllegalStateException();

DynamicArray.this.remove(this.cursor);

this.cursor--;

}

@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));

}

}

}

/**

* 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);

}

}

}