package 集合.list.ArrayList;
import java.util.Arrays;
import java.util.Date;
public class MyArryList {
//定义一个空的数组
private final static Object[] myArray = {};
//定义一个默认长度10
private final static int default_length = 10;
Object[] elementData;
//myArryList长度
private int size = 0;
//无参数构造方法,默认容量10
public MyArryList() {
this.elementData = myArray;
}
//带参数构造函数
public MyArryList(int length) {
if (length < 0) {
throw new IllegalArgumentException("参数不能小于0");
}
this.elementData = new Object[length];
size = length;
}
//获取长度
public int getSize() {
return this.size;
}
//添加元素
public void add(Object args) {
//每次添加元素时需要考虑长度问题
//判断是否需要扩容
if (size >= elementData.length) {
this.grown();
}
elementData[size++] = args;
}
//扩容方法
private void grown() {
if (elementData.length <= 1) {
elementData = Arrays.copyOf(elementData, elementData.length + 1);
} else {
elementData = Arrays.copyOf(elementData, elementData.length + (elementData.length >> 1));
}
}
//删除元素
public void remove(Object obj) {
//先查找第一次出现的索引
int i = indexOf(obj);
if (i != -1) {
remove(i);
}
}
//删除指定索引位置元素
public void remove(int index) {
if (index < 0 || index > size) {
throw new IndexOutOfBoundsException("参数越界");
}
//遍历数组
//for(int i = index;i<elementData.length;i++){
// elementData[i]=elementData[i+1];
//}
System.arraycopy(elementData, index + 1, elementData, index, size - index - 1);
size--;
}
//指定索引插入元素
public void insert(int index, Object obj) {
if (index < 0 || index > size) {
throw new IndexOutOfBoundsException("参数越界");
}
//
if (size >= elementData.length) {
this.grown();
}
//[1,2,3,4][1,2,5,3,4]第一种方式
// System.arraycopy(elementData,index, elementData,index-1,size-index);
//遍历数组
for (int i = size - 1; i >= index; i--) {
elementData[i + 1] = elementData[i];
}
//将需要插入元素放入指定索引位置
elementData[index] = obj;
size++;
}
//查找元素第一次索引
public int indexOf(Object obj) {
for (int i = 0; i < size; i++) {
if (elementData[i] == obj || elementData[i] != null && elementData[i].equals(obj)) {
return i;
}
}
return -1;
}
//更改元素
public void set(int index, Object obj) {
elementData[index] = obj;
}
//清空数据
public void clear() {
elementData = new Object[0];
size = 0;
}
//判断索引是否越界
public boolean out(int index) {
if (index < 0 || index > size) {
return false;
} else return true;
}
//判断是否包含
public boolean contains(Object obj) {
return indexOf(obj) != -1;
}
//判断是否为空
public boolean isEmpty() {
return size == 0;
}
//截取子列表
public MyArryList sublist(int fromIndex, int toIdex) {
if (fromIndex < 0 || toIdex > size) {
throw new IndexOutOfBoundsException("越界");
}
if (fromIndex > toIdex) {
throw new IllegalArgumentException();
}
MyArryList sublist = new MyArryList(toIdex - fromIndex);
System.arraycopy(elementData, fromIndex, sublist, 0, toIdex - fromIndex);
sublist.size = toIdex - fromIndex;
return sublist;
}
//toString重写
@Override
public String toString() {
Object[] newstring =new Object[size];
System.arraycopy(elementData, 0, newstring, 0, size);
return Arrays.toString(newstring);
}
}
原文：https://blog.51cto.com/12013190/2430394