Java中SJBArrayList自己简单实现ArrayList

/**

* 自己实现ArrayList

* @author zyyt

*

*/

public class SJBArrayList {

//存放SJBArrayList中的元素

transient Object[] elementData;

//SJBArrayList中含有多少个元素

private int size;

//构造方法

public SJBArrayList(){

this(10);

}

public SJBArrayList(int initialCapacity)

{   //对elementData进行初始化

if (initialCapacity > 0) {

this.elementData = new Object[initialCapacity];

} else if (initialCapacity == 0) {

this.elementData = new Object[0];

} else {

throw new IllegalArgumentException("Illegal Capacity: "+

initialCapacity);

}

}

//判断这个SJBArrayList是否包含元素，如果不包含元素返回true 如果包含则返回false

public boolean isEmpty(){

return size == 0;

}

//返回这个SJBArrayList中包含的元素的个数

public int size(){

return size;

}

//添加一个元素

public void add(Object obj)

{

if(size == elementData.length){

Object[] array = new Object[size * 2 +1];

System.arraycopy(elementData, 0, array, 0, elementData.length);

elementData = array;

}

elementData[size++] = obj;

}

//获取对应索引中的元素

public Object get(int index){

if(index<0 || index >= size){

System.out.println("index超过最大索引值或者index小于0");

return null;

}

return elementData[index];

}

//删除对应索引的值

public Object remove(int index){

if(index < 0 || index > size){

System.out.println("index小于0，或者越界");

System.exit(0);

}

Object oldValue = this.get(index);

System.arraycopy(elementData, index + 1,elementData, index, size);

elementData[size--] = null;

return oldValue;

}

//提货对应索引中的值

public Object set(int index,Object obj)

{

if(index < 0 || index > size){

System.out.println("index小于0，或者越界");

System.exit(0);

}

Object oldValue = this.get(index);

elementData[index] = obj;

return oldValue;

}

//清空SJBArrayList

public void clear(){

for(int i=0;i<size;i++){

elementData[i] = null;

}

size = 0;

}

public static void main(String[] args){

SJBArrayList sjbList = new SJBArrayList();

sjbList.add("111");

sjbList.add("2222");

sjbList.add("3333");

sjbList.add("4444");

sjbList.add("5555");

sjbList.add("66666");

sjbList.remove(2);

System.out.println(sjbList.get(3));

for(int i=0;i<sjbList.size();i++){

System.out.println(sjbList.get(i));

}

}

}