实现一个简单的数组结构

实现一个简单的数组结构，有如下功能

• 获取size
• 判断数组是否为空
• 添加元素
• 向头部添加元素
• 获取元素
• 指定位置设置值
• 判断是否包含指定元素
• 查找元素在数组中的下标
• 获取数组中第一个元素的值
• 获取数组中最后一个元素的值
• 移除指定位置的元素
• 移除数组中第一个位置的元素
• 移除数组中最后一个位置的元素
• 移除指定元素

练习源码

/**
 * 数组
 */
public class Array<E> {

    private E[] data;
    private int size;

    public Array(int capacity) {
        data = (E[]) new Object[capacity];
        size = 0;
    }

    /**
     * 无参构造函数，默认数组长度10
     */
    public Array() {
        this(10);
    }

    public int getSize() {
        return size;
    }

    public int getCapacity() {
        return data.length;
    }

    public boolean isEmpty() {
        return size == 0;
    }

    public void addLast(E e) {
        add(size, e);
    }

    public void addFirst(E e) {
        add(0, e);
    }

    public void add(int index, E e) {
        if (index < 0 || index > size) {
            throw new IllegalArgumentException("Add failed. Require index >= 0 and <= size.");
        }
        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++;
    }

    public E get(int index) {
        if (index < 0 || index >= size) {
            throw new IllegalArgumentException("Get failed. Index is illegal.");
        }
        return data[index];
    }

    public void set(int index, E e) {
        if (index < 0 || index >= size) {
            throw new IllegalArgumentException("Set failed. Index is illegal.");
        }
        data[index] = e;
    }

    public boolean contains(E e) {
        for (int i = 0; i < size; i++) {
            if (data[i] == e) {
                return true;
            }
        }
        return false;
    }

    public int find(E e) {
        for (int i = 0; i < size; i++) {
            if (data[i].equals(e)) {
                return i;
            }
        }
        return -1;
    }

    public E getLast() {
        return get(size - 1);
    }

    public E getFirst() {
        return get(0);
    }

    public E remove(int index) {
        if (index < 0 || index >= size) {
            throw new IllegalArgumentException("Remove failed. Index is illegal.");
        }
        E temp = data[index];
        for (int i = index + 1; i < size; i++) {
            data[i - 1] = data[i];
        }
        size--;
        if (size == data.length / 2 && data.length / 2 != 0) {
            resize(data.length / 2);
        }
        return temp;
    }

    public E removeFirst() {
        return remove(0);
    }

    public E removeLast() {
        return remove(size - 1);
    }

    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;
    }
}