Array.java

package struct.array;

/**
 * 数组
 * 插入元素（头部、尾部、指定下角标）
 * 删除元素（头部、尾部、指定下角标）
 * 扩容
 *
 * @param <T>
 */
public class Array<T> {

    private T[] data;
    private int size;

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

    public Array() {
        this(10);
    }

    public static void main(String[] args) {
        Array arr = new Array(5);
        arr.add(0, 0);
        arr.add(1, 0);
        arr.add(2, 0);
        arr.add(3, 0);
        arr.add(4, 0);
        arr.add(5, 0);
        arr.remove(4);
        arr.remove(3);

    }

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

    public int count() {
        return size;
    }

    public void set(int index, T e) {
        checkIndex(index);
        data[index] = e;
    }

    public T get(int index) {
        checkIndex(index);
        return data[index];
    }

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

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

    public void add(int index, T e) {
        checkIndex(index);

        if (size == data.length) {
            resize(data.length * 2);
        }

        for (int i = size - 1; i >= index; i--) {
            data[i + 1] = data[i];
        }

        data[index] = e;
        size++;
    }

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

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

    public T remove(int index) {
        checkIndexForRemove(index);

        T result = data[index];
        for (int i = index + 1; i < size; i++) {
            data[i - 1] = data[i];
        }

        size--;
        data[size] = null;

        if (size == data.length / 4 && data.length / 2 != 0) {
            resize(data.length / 2);
        }

        return result;
    }

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

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

    public void removeElement(T e) {
        int index = find(e);
        if (index != -1) {
            remove(index);
        }
    }

    private void resize(int capacity) {
        T[] newData = (T[]) new Object[capacity];

        for (int i = 0; i < size; i++) {
            newData[i] = data[i];
        }
        data = newData;
    }

    private void checkIndex(int index) {
        if (index < 0 || index > size) {
            throw new IllegalArgumentException("Add failed! Require index >=0 and index <= size.");
        }
    }

    private void checkIndexForRemove(int index) {
        if (index < 0 || index >= size) {
            throw new IllegalArgumentException("remove failed! Require index >=0 and index < size.");
        }
    }

}