package com.wang.list;import java.util.Iterator;public class MyArrayList<T> implements Iterable<T> {//初始化集合的容量private static final int DEFAULT_CAPACITY=10;//当前元素的个数private int theSize;//使用一个数组来实现这个Listprivate T [] theItems;public MyArrayList(){clear();}//清空集合元素,初始化时使用public void clear(){theSize=0;ensureCapacity(DEFAULT_CAPACITY);}//通过传入的int值大小决定是否需要扩充集合空间大小public void ensureCapacity(int newCapacity) {if(newCapacity<theSize)return;T[] old=theItems;theItems=(T[]) new Object[newCapacity];for(int i=0;i<size();i++){theItems[i]=old[i];}}//返回当前集合元素的个数public int size() {return theSize;}//返回当前集合是否为空public boolean isEmpty(){return size()==0;}public void trimToSize(){ensureCapacity(size());}//获取指定索引下的元素值public T get(int index){if(index<0||index>=size())throw new ArrayIndexOutOfBoundsException("索引越界");return theItems[index];}//修改指定索引上的元素值public T set(int index,T value){if(index<0||index>=size())throw new ArrayIndexOutOfBoundsException("索引越界");T old=theItems[index];theItems[index]=value;return old;}//添加元素,直接指定元素,默认添加在数组末尾public boolean add(T value){add(size(),value);return true;}//添加元素,指定添加位置和元素值public void add(int index, T value) {//如果数组元素个数已经达到指定size();那么扩展该数组,使数组容量加倍if(theItems.length==size()){ensureCapacity(size()*2+1);}//从末尾元素向前遍历,一直到index处,使index处之后的所有元素向后移动一位for(int i=theSize;i>index;i--){theItems[i]=theItems[i-1];}theItems[index]=value;//添加完元素,是集合元素个数加一theSize++;}//移除指定索引处的元素值,public T remove(int index){T val=theItems[index];for(int i=index;i<size()-1;i++){theItems[i]=theItems[i+1];}theSize--;return val;}//重写迭代器的方法,使用下面的静态内部类实现,注意static,如果没有该关键字,会使内部类访问不到外部的成员
    @Overridepublic Iterator<T> iterator() {return new ArrayListIterator();}private class ArrayListIterator implements java.util.Iterator<T>{private int current=0;@Overridepublic boolean hasNext() {return current<size();}@Overridepublic T next() {return theItems[current++];}@Overridepublic void remove() {MyArrayList.this.remove(--current);}}}

package com.wang.list;import java.util.Iterator;public class TestMyArrayList {public static void main(String[] args) {MyArrayList<String> list=new MyArrayList<>();list.add("hello");list.add("world");list.add("I");list.add("am");list.add("a");list.add("list");System.out.println("List的元素个数为:"+list.size());System.out.println("list的第二个元素个数为:"+list.get(1));//将第5个元素"a",替换为"the".list.set(4, "the");System.out.println("替换后的第五个元素为:"+list.get(4));//使用iterator方式遍历ListIterator<String> it = list.iterator();while(it.hasNext()){System.out.println(it.next());}}
}

package com.wang.list;import java.util.Iterator;public class MyLinkedList<T> implements Iterable<T> {//保存元素个数private int theSize;//记录修改的次数,//用处是:用于在迭代器遍历时,用于判断在迭代过程中是否发生了修改操作,如果发生了修改,则抛出异常private int modCount=0;//定义两个节点,首节点和尾节点private Node<T> begin;private Node<T> end;public MyLinkedList(){clear();}//初始化一个空表public void clear(){begin=new Node<T>(null, null, null);end=new Node<T>(null, begin, null);begin.next=end;theSize=0;modCount++;}public int size(){return theSize;}public boolean isEmpty(){return size()==0;}public boolean add(T value){add(size(),value);return true;}public void add(int index,T value){//在指定索引位置先找到那个索引处的节点类信息即先getNode(index).然后执行addBefore方法
        addBefore(getNode(index),value);}//在指定的那个节点P的前方插入值为value的一个元素private void  addBefore(Node<T> p,T value){Node<T> newNode=new Node<T>(value, p.prev, p);newNode.prev.next=newNode;p.prev=newNode;theSize++;modCount++;}//通过索引值返回对应位置的节点类信息private Node<T> getNode(int index){Node<T> p;if(index<0||index>size()){throw new IndexOutOfBoundsException();}if(index<(size()/2)){p=begin.next;for(int i=0;i<index;i++){p=p.next;}}else{p=end;for(int i=size();i>index;i--){p=p.prev;}}return p;}//返回指定索引处的元素值public T get(int index){return getNode(index).data;}//将指定所引处的元素值修改为valuepublic T set(int index,T value){Node<T> p=getNode(index);T oldData=p.data;p.data=value;return oldData;}//移除指定索引处的元素值public T remove(int index){return remove(getNode(index));}private T remove(Node<T> p){p.next.prev=p.prev;p.prev.next=p.next;theSize--;modCount++;return p.data;}@Overridepublic Iterator<T> iterator() {return new LinkedListIteraor();}private  class LinkedListIteraor implements Iterator<T>{//保留第一个起始位置的节点private Node<T> current=begin.next;//记录此刻集合修改的总次数,之后会拿modCount再和此值作比较,如果不相等,说明在迭代过程中,//集合发生了修改操作,则会抛出异常private int exceptedModCount=modCount;//判断是否可以向后移动指针private boolean canMove=false;@Overridepublic boolean hasNext() {return current!=end;}@Overridepublic T next() {if(exceptedModCount!=modCount){throw new java.util.ConcurrentModificationException();}if(!hasNext()){throw new java.util.NoSuchElementException();}T nextValue=current.data;current=current.next;canMove=true;return nextValue;}@Overridepublic void remove() {if(exceptedModCount!=modCount){throw new java.util.ConcurrentModificationException();}if(!canMove){throw new IllegalStateException();}MyLinkedList.this.remove(current.prev);canMove=false;exceptedModCount++;}}private static class Node<T> {//当前节点数据public T data;//到前一个节点的链public Node<T> prev;//到后一个节点的链public Node<T> next;public Node(T data, Node<T> prev, Node<T> next) {this.data = data;this.prev = prev;this.next = next;}}}

package com.wang.list;import java.util.Iterator;public class TestMyLinkedList {public static void main(String[] args) {MyLinkedList<Integer> list=new MyLinkedList<>();list.add(1);list.add(5);list.add(7);list.add(6);list.add(4);list.add(2);list.add(3);for(int i=0;i<list.size();i++){System.out.print(list.get(i)+" ");}System.out.println();list.set(2, 8);list.remove(0);Iterator<Integer> it = list.iterator();while(it.hasNext()){System.out.print(it.next()+" ");}}}

for(Integer i:list){if(i==6){list.remove(6);}
}

Iterator<Integer> it = list.iterator();while(it.hasNext()){if(it.next()==6){it.remove();}}