Java での動的配列の具体的な実装

//向指定位置添加元素e
	public void add(int index,E e){
		if(index<0||index>size){
			throw new IllegalArgumentException("AddLast failed.Require index error");

		}
		if(size == data.length){
			resize(2*data.length);
		}
		
		for (int i = size-1; i >= index; i--) {
			data[i+1] = data[i];
		}
		data[index] = e;
		size++;
	}

//删除元素,并返回被删除的元素
	public E remove(int index){
		if(index<0 || index >=size){
			throw new IllegalArgumentException("Remove failed. Index is illegal");
		}
		E ret = data[index];
		for (int i = index+1; i < size; i++) {
			data[i-1] = data[i];
		}
		size--;
		data[size] = null;//loitering objects  != memory leak
		
		if(size == data.length /4 && data.length/2 != 0){
			resize(data.length/2);
		}
		return ret;
	}

private void resize(int newCapacity){
		E[] newData = (E[])new Object[newCapacity];
		for (int i = 0; i < size; i++) {
			newData[i] = data[i];
		}
		data = newData;
	}

package array;
public class Array {
	private E[] data;
	private int size;
	@SuppressWarnings("unchecked")
	public Array(int capacity){
		data = (E[]) new Object[capacity];
		size = 0;
	}
	public Array(){
		this(10);
	}
	public int getSize(){
		return size;
	}
	public int getCapacity(){
		return data.length;
	}
	public boolean isEmpty(){
		return size == 0;
	}
	//向第一个位置添加一个元素
	public void addFirst(E e){
		add(0,e);
	}
	//向最后一个位置添加一个元素
	public void addLast(E e){
		add(size,e);
	}
	//向指定位置添加元素e
	public void add(int index,E e){
		if(index<0||index>size){
			throw new IllegalArgumentException("AddLast failed.Require index error");
		}
		if(size == data.length){
			resize(2*data.length);
		}
		for (int i = size-1; i >= index; i--) {
			data[i+1] = data[i];
		}
		data[index] = e;
		size++;
	}
	//获取index位置的元素e
	public E get(int index){
		if(index<0 || index >=size){
			throw new IllegalArgumentException("Get failed. Index is illegal");
		}
		return data[index];
	}
	//修改index索引位置的元素e
	public void set(int index, E e){
		if(index<0 || index >=size){
			throw new IllegalArgumentException("Get failed. Index is illegal");
		}
		data[index] = e;
	}
	//判断元素是否存在于数组中
	public boolean contains(E e){
		for (int i = 0; i < size; i++) {
			if(data[i].equals(e)){
				return true;
			}
		}
		return false;
	}
	//找到元素并返回索引
	public int find(E e){
		for (int i = 0; i < size; i++) {
			if(data[i].equals(e)){
				return i;
			}
		}
		return -1;
	}
	//删除元素,并返回被删除的元素
	public E remove(int index){
		if(index<0 || index >=size){
			throw new IllegalArgumentException("Remove failed. Index is illegal");
		}
		E ret = data[index];
		for (int i = index+1; i < size; i++) {
			data[i-1] = data[i];
		}
		size--;
		data[size] = null;//loitering objects  != memory leak
		
		if(size == data.length /4 && data.length/2 != 0){
			resize(data.length/2);
		}
		return ret;
	}
	public E removeFirst(){
		return remove(0);
	}
	public E removeLast(){
		return remove(size-1);
	}
	//从数组中删除元素e
	public void removeElement(E e){
		int index = find(e);
		if(index != -1){
			remove(index); 
		}
	}
	@Override
	public String toString(){
		StringBuilder res = new StringBuilder();
		res.append(String.format("Array:size = %d ,capacity = %d\n",size,data.length));
		res.append('[');
		for (int i = 0; i < size; i++) {
			res.append(data[i]);
			if(i != size-1){
				res.append(",");
			}
		}
		res.append(']');
		return res.toString();
	}
	private void resize(int newCapacity){
		E[] newData = (E[])new Object[newCapacity];
		for (int i = 0; i < size; i++) {
			newData[i] = data[i];
		}
		data = newData;
	}
}

package array;

public class Main {
	public static void main(String[] args){
		Array<Integer> arr = new Array<>();
		for (int i = 0; i < 10; i++) {
			arr.addLast(i);
		}
		System.out.println(arr);
		arr.add(1, 100);
		System.out.println(arr);
		arr.addFirst(-1);
		System.out.println(arr);
		arr.set(0, 1);
		System.out.println(arr);
	}
}