模擬ArrayList底層實現

package chengbaoDemo; import java.util.ArrayList; import java.util.Arrays; import comman.Human; /** * ArrayList 底層實現 */
public class MyArrayList { /** * The value is used for Object Stroage. */
    private Object value[]; /** *The size is the number of Object used. */

    private int size; public MyArrayList() { // value = new Object[10];
        this(10); } public MyArrayList(int size) { value = new Object[size]; } /** *Get the number of array's element */
    public int size() { return size; } public boolean isEmpty() { return size == 0; } /** *add element into the object storage. */
    public void add(Object obj) { value[size] = obj; size++; //擴容
        if (size >= value.length) { ensureCapacity(); } } /** *擴容 */
    public void ensureCapacity() { int newLength = value.length * 2 + 2; Object newObj[] = Arrays.copyOf(value, newLength); value = newObj; } /** *Get the element from the object storage. */
    public Object get(int size) { rangeCheck(size); return value[size]; } /** * Check whether occured out of bound Exception */ 
    public void  rangeCheck(int index) { if (index < 0 || index > value.length) { try { throw new Exception(); } catch (Exception e) { e.printStackTrace(); } } } /** * Return the index of the first occurrence of the specfied element in this value, * or -1 if the value does not contains the specfied element. */
    public int indexOf(Object obj) { if (obj == null) { for (int i = 0 ; i < value.length; i++) { if (value[i] == null) { return i; } } return -1; }else { for (int i = 0; i < value.length; i++) { if (value[i].equals(obj)) { return i; } } return -1; } } /** *Repaces the element at the specfied position in this object array *with the specfied element. */
    public Object set(int index, Object obj) { rangeCheck(index); Object oldObj = value[index]; value[index] = obj; return oldObj; } public void printf() { for (int i = 0; i < size; i++) { System.out.println(value[i]); } } ///測試
    public static void main(String[] args) { MyArrayList mal = new MyArrayList(3); mal.add("asd"); mal.add("qwe"); mal.add("asd"); mal.add("qwe"); Human h = new Human("成寶"); mal.add(h); System.out.println(mal.size()); Human hs = (Human)mal.get(4); System.out.println(hs.getName()); mal.add(null); System.out.println(mal.get(5)); System.out.println(mal.indexOf(null)); mal.printf(); mal.set(5, 90); mal.printf(); } }