mirror of
https://github.com/TheAlgorithms/Java.git
synced 2025-07-09 12:11:28 +08:00
Huayang Sun
@ -11,206 +11,203 @@ import java.util.stream.StreamSupport;
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* @param <E> the type that each index of the array will hold
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* @param <E> the type that each index of the array will hold
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*/
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*/
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public class DynamicArray<E> implements Iterable<E> {
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public class DynamicArray<E> implements Iterable<E> {
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private static final int DEFAULT_CAPACITY = 16;
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private int capacity;
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private int capacity;
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private int size;
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private int size;
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private Object[] elements;
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private Object[] elements;
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/**
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/**
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* constructor
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* constructor
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*
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*
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* @param capacity the starting length of the desired array
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* @param capacity the starting length of the desired array
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*/
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*/
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public DynamicArray(final int capacity) {
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public DynamicArray(final int capacity) {
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this.size = 0;
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this.size = 0;
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this.capacity = capacity;
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this.capacity = capacity;
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this.elements = new Object[this.capacity];
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this.elements = new Object[this.capacity];
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}
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}
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/** No-args constructor */
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/**
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public DynamicArray() {
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* No-args constructor
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this.size = 0;
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*/
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this.capacity = 10;
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public DynamicArray() {
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this.elements = new Object[this.capacity];
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this(DEFAULT_CAPACITY);
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}
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}
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/**
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/**
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* Doubles the capacity of the array
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* Adds an element to the array If full, creates a copy array twice the size of the current one
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*
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*
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* @return int the new capacity of the array
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* @param element the element of type <E> to be added to the array
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*/
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*/
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public int newCapacity() {
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public void add(final E element) {
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this.capacity *= 2;
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if (this.size == this.elements.length) {
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// changed from this.capacity <<= 1; now much easier to understand
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this.elements = Arrays.copyOf(this.elements, newCapacity(2 * this.capacity));
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return this.capacity;
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}
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}
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/**
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this.elements[this.size] = element;
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* Adds an element to the array If full, creates a copy array twice the size of the current one
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size++;
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*
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}
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* @param element the element of type <E> to be added to the array
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*/
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public void add(final E element) {
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if (this.size == this.elements.length) {
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this.elements = Arrays.copyOf(this.elements, newCapacity());
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}
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this.elements[this.size] = element;
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/**
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size++;
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* Places element of type <E> at the desired index
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}
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*
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* @param index the index for the element to be placed
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* @param element the element to be inserted
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*/
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public void put(final int index, E element) {
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this.elements[index] = element;
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}
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/**
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/**
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* Places element of type <E> at the desired index
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* get method for element at a given index returns null if the index is empty
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*
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*
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* @param index the index for the element to be placed
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* @param index the desired index of the element
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* @param element the element to be inserted
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* @return <E> the element at the specified index
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*/
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*/
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public void put(final int index, E element) {
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public E get(final int index) {
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this.elements[index] = element;
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return getElement(index);
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}
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}
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/**
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/**
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* get method for element at a given index returns null if the index is empty
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* Removes an element from the array
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*
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*
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* @param index the desired index of the element
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* @param index the index of the element to be removed
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* @return <E> the element at the specified index
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* @return <E> the element removed
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*/
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*/
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public E get(final int index) {
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public E remove(final int index) {
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return getElement(index);
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final E oldElement = getElement(index);
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}
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fastRemove(this.elements, index);
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/**
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if (this.capacity > DEFAULT_CAPACITY && size * 4 <= this.capacity)
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* Removes an element from the array
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this.elements = Arrays.copyOf(this.elements, newCapacity(this.capacity / 2));
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*
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return oldElement;
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* @param index the index of the element to be removed
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}
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* @return <E> the element removed
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*/
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public E remove(final int index) {
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final E oldElement = getElement(index);
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fastRemove(this.elements, index);
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return oldElement;
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/**
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}
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* get method for size field
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*
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* @return int size
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*/
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public int getSize() {
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return this.size;
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}
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/**
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/**
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* get method for size field
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* isEmpty helper method
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*
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*
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* @return int size
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* @return boolean true if the array contains no elements, false otherwise
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*/
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*/
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public int getSize() {
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public boolean isEmpty() {
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return this.size;
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return this.size == 0;
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}
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}
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/**
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public Stream<E> stream() {
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* isEmpty helper method
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return StreamSupport.stream(spliterator(), false);
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*
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}
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* @return boolean true if the array contains no elements, false otherwise
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*/
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public boolean isEmpty() {
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return this.size == 0;
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}
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public Stream<E> stream() {
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private void fastRemove(final Object[] elements, final int index) {
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return StreamSupport.stream(spliterator(), false);
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final int newSize = this.size - 1;
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}
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private void fastRemove(final Object[] elements, final int index) {
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if (newSize > index) {
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final int newSize = this.size - 1;
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System.arraycopy(elements, index + 1, elements, index, newSize - index);
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}
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if (newSize > index) {
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elements[this.size = newSize] = null;
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System.arraycopy(elements, index + 1, elements, index, newSize - index);
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}
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}
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elements[this.size = newSize] = null;
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private E getElement(final int index) {
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}
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return (E) this.elements[index];
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}
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private E getElement(final int index) {
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private int newCapacity(int capacity) {
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return (E) this.elements[index];
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this.capacity = capacity;
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}
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return this.capacity;
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}
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/**
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/**
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* returns a String representation of this object
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* returns a String representation of this object
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*
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*
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* @return String a String representing the array
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* @return String a String representing the array
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*/
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*/
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@Override
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@Override
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public String toString() {
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public String toString() {
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return Arrays.toString(Arrays.stream(this.elements).filter(Objects::nonNull).toArray());
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return Arrays.toString(Arrays.stream(this.elements).filter(Objects::nonNull).toArray());
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}
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}
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/**
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/**
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* Creates and returns a new Dynamic Array Iterator
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* Creates and returns a new Dynamic Array Iterator
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*
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*
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* @return Iterator a Dynamic Array Iterator
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* @return Iterator a Dynamic Array Iterator
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*/
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*/
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@Override
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@Override
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public Iterator iterator() {
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public Iterator iterator() {
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return new DynamicArrayIterator();
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return new DynamicArrayIterator();
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}
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}
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private class DynamicArrayIterator implements Iterator<E> {
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private class DynamicArrayIterator implements Iterator<E> {
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private int cursor;
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private int cursor;
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@Override
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@Override
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public boolean hasNext() {
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public boolean hasNext() {
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return this.cursor != size;
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return this.cursor != size;
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}
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}
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@Override
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@Override
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public E next() {
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public E next() {
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if (this.cursor > DynamicArray.this.size) throw new NoSuchElementException();
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if (this.cursor > DynamicArray.this.size) throw new NoSuchElementException();
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if (this.cursor > DynamicArray.this.elements.length)
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if (this.cursor > DynamicArray.this.elements.length)
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throw new ConcurrentModificationException();
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throw new ConcurrentModificationException();
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final E element = DynamicArray.this.getElement(this.cursor);
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final E element = DynamicArray.this.getElement(this.cursor);
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this.cursor++;
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this.cursor++;
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return element;
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return element;
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}
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}
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@Override
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@Override
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public void remove() {
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public void remove() {
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if (this.cursor < 0) throw new IllegalStateException();
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if (this.cursor < 0) throw new IllegalStateException();
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DynamicArray.this.remove(this.cursor);
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DynamicArray.this.remove(this.cursor);
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this.cursor--;
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this.cursor--;
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}
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}
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@Override
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@Override
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public void forEachRemaining(Consumer<? super E> action) {
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public void forEachRemaining(Consumer<? super E> action) {
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Objects.requireNonNull(action);
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Objects.requireNonNull(action);
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for (int i = 0; i < DynamicArray.this.size; i++) {
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for (int i = 0; i < DynamicArray.this.size; i++) {
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action.accept(DynamicArray.this.getElement(i));
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action.accept(DynamicArray.this.getElement(i));
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}
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}
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}
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}
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}
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}
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/**
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/**
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* This class is the driver for the DynamicArray<E> class it tests a variety of methods and prints
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* This class is the driver for the DynamicArray<E> class it tests a variety of methods and prints
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* the output
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* the output
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*/
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*/
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public static void main(String[] args) {
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public static void main(String[] args) {
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DynamicArray<String> names = new DynamicArray<>();
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DynamicArray<String> names = new DynamicArray<>();
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names.add("Peubes");
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names.add("Peubes");
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names.add("Marley");
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names.add("Marley");
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for (String name : names) {
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for (String name : names) {
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System.out.println(name);
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System.out.println(name);
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}
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}
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names.stream().forEach(System.out::println);
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names.stream().forEach(System.out::println);
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System.out.println(names);
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System.out.println(names);
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System.out.println(names.getSize());
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System.out.println(names.getSize());
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names.remove(0);
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names.remove(0);
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for (String name : names) {
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for (String name : names) {
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System.out.println(name);
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System.out.println(name);
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}
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}
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}
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}
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}
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}
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