DynamicArray.java

package com.anthonynsimon.datastructures;

import java.util.Arrays;

public class DynamicArray<E> {

    private final int growthFactor = 2;
    protected int size;
    protected E[] data;

    public DynamicArray(int initialCapacity) {
        this.size = 0;
        // It is safe to suppress unchecked exception because the array we're creating
        // is of the same type as the one passed.
        @SuppressWarnings("unchecked")
        E[] array = (E[]) new Object[initialCapacity];
        this.data = array;
    }

    public void add(E item) {
        ensureCapacity();
        this.data[size()] = item;
        this.size++;
    }

    public E get(int index) throws IndexOutOfBoundsException {
        if (isOutOfBounds(index)) {
            throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + capacity());
        }
        return this.data[index];
    }

    public void set(int index, E item) throws IndexOutOfBoundsException {
        if (isOutOfBounds(index)) {
            throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + capacity());
        }
        this.data[index] = item;
    }

    public int capacity() {
        return this.data.length;
    }

    public int size() {
        return this.size;
    }

    private boolean isOutOfBounds(int index) {
        return index < 0 || index > capacity() - 1;
    }

    private void ensureCapacity() {
        if (capacity() < size() + 1) {
            int newCapacity = capacity() * this.growthFactor;
            this.data = Arrays.copyOf(this.data, newCapacity);
        }
    }
}