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));
}
}
}
