java学习容器

自己模拟ArrayList:

 private Object[] elementData;

    private int size;

    // 可以指定集合大小,默认10
    public MyArrayList(int initialCapacity) {
    if (initialCapacity < 0) {
        try {
        throw new IllegalArgumentException("Illegal Capacity: " + initialCapacity);
        } catch (Exception e) {
        e.printStackTrace();
        }
    }
    elementData = new Object[initialCapacity];
    }

    // 无参构造
    public MyArrayList() {
    this(10);
    }

    // 返回集合大小
    public int size() {
    return size;
    }

    // 返回集合大小
    public boolean isEmpty() {
    return size == 0;
    }

    // 根据索引获取对象
    public Object get(int index) {
    rangeCheck(index);
    return elementData[index];
    }

    // 添加元素
    public void add(Object object) {
    ensureCapacity();
    elementData[size++] = object;
    }

    // 根据索引删除
    public void remove(int index) {
    rangeCheck(index);
    int numMoved = size - index - 1;
    if (numMoved > 0)
        System.arraycopy(elementData, index + 1, elementData, index, numMoved);
    elementData[--size] = null;
    }

    // 根据对象删除
    public void remove(Object object) {
    for (int i = 0; i < size; i++) {
        if (get(i).equals(object)) {
        remove(i);
        }
    }
    }

    // 替换
    public Object set(int index, Object object) {
    rangeCheck(index);
    Object oldValue = elementData[index];
    elementData[index] = object;
    return oldValue;
    }

    public void add(int index, Object obj) {
    rangeCheck(index);
    ensureCapacity(); // 数组扩容
    System.arraycopy(elementData, index, elementData, index + 1, size - index);
    elementData[index] = obj;
    size++;
    }

    // 数组扩容和数据的拷贝
    private void ensureCapacity() {
    if (size == elementData.length) {
        Object newArray[] = new Object[size * 2 + 1];
        System.arraycopy(elementData, 0, newArray, 0, elementData.length);
        elementData = newArray;
    }
    }

    // 封装判断index是否合法
    private void rangeCheck(int index) {
    if (index >= size) {
        try {
        throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
        } catch (Exception e) {
        e.printStackTrace();
        }
    }
    }

    public static void main(String[] args) {
    MyArrayList list = new MyArrayList();
    list.add("333");
    list.add("444");
    list.add("555");
    list.add("344433");
    list.add("222");
    list.add("666");
    list.remove("5");
    list.set(0, "4432432");
    list.add(5, "111");
    System.out.println(list.size);
    // System.out.println(list.get(6));
    }