package chengbaoDemo;import java.util.ArrayList;
import java.util.Arrays;import comman.Human;
/*** ArrayList 底层实现*/
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++;//扩容if (size >= value.length) {ensureCapacity();}}/***扩容 */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]);}}///测试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("成宝");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();}}