小伙伴来自己实现一个ArrayList

想来去年实习面试的时候，有公司发来面试题，要求自己实现一个List，当时觉得好难好难，现工作了，有空回来补习一下数据结构，在此与各位小伙伴共勉，望大家多多指教。

代码如下：

package com.david.duan;

import java.util.Iterator;
import java.util.NoSuchElementException;

public class MyArrayList implements Iterable<Student>{

//给List设定默认大小
private static final int DEFAULT_SIZE = 10;
//用于存储list的大小
private int size;
//原生数组
private Student [] students;
//构造函数
public MyArrayList () {
clear ();
}

private void clear() {
size = 0;
ensureCapacity(DEFAULT_SIZE);
}

public int size () {
return size;
}

public boolean isEmplty () {
return size() == 0;
}

public void trimToSize () {
ensureCapacity (size());
}
//返回固定下标的元素
public Student get (int idx) {
if ( idx < 0 || idx >= size()  )
throw new ArrayIndexOutOfBoundsException();
return students[idx];
}
//在固定位置插入元素，并返回之前的元素
public Student set (int idx, Student news) {
if ( idx < 0 || idx >= size()  )
throw new ArrayIndexOutOfBoundsException();
Student oldStudent  = students[idx];
students[idx] = news;
return oldStudent;
}
//当增加元素到list时，如果数组长度不够，用此扩充大小
public void ensureCapacity (int newCapacity) {
if (newCapacity < size)
return;
Student [] oldStudents = students;
students = (Student []) new Object[newCapacity];
for (int i = 0; i < size(); i++) {
students[i] = oldStudents[i];
}

}

public boolean add(Student student) {
add(size(), student);
return true;
}

public void add (int idx, Student student) {
if (students.length == size())
ensureCapacity(size() * 2 +1);
for (int i = size; i > idx; i--)
students[i] = students [i -1];
students [idx] = student;

size ++;
}
//删除元素
public Student remove(int idx) {
Student removeStudent = students[idx];
for (int i = idx; i < size; i++) {
students [i] = students[i+1];
}
size --;
return removeStudent;
}

//实现迭代器接口
@Override
public Iterator<Student> iterator() {
return new ArrayListIterator();
}
private class ArrayListIterator implements java.util.Iterator<Student> {

private int current = 0;

@Override
public boolean hasNext() {
return current < size();
}

@Override
public Student next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
return students[current +1];
}

@Override
public void remove() {
MyArrayList.this.remove( --current);
}

}
}

以上的实现基本仿造ArrayList的源码实现，但由于水平有限，很多细节考虑不周，望小伙伴们多多包涵。Collection的API存在某种错误检测以保证合理的限界，为了把精力放在编写迭代器的基本方面，小鸟并没有检测可能使得迭代器结构无效的修改，也没有检测非法的迭代器remove方法。如果有机会，我会在接下来的LinkedList实现中把他完善，谢谢小伙伴们的继续支持。