Java Iterator模式 模仿Collectin ArrayList LinckedList
Java Iterator模式 Java Iterator模式, 模仿Collectin ArrayList LinckedList一、有如下几个类
1.接口Collection.java
2.接口Iterator.java
3.ArrayList.java
4.LinkedList.java
5.Node.java
关系如下：
代码如下：
1.接口Collection.javapublic interface Collection<E> {
public void add(E e);
public int size();
public Iterator iterator();
}2.ArrayList.javapublic class ArrayList<E> implements Collection<E>{
//先给定一个长度为10的数组
Object [] objects = new Object;
//冗余一个int指数，方便判定是组是否为满和返回集合大小
int index = 0;
@Override
//1.动态添加元素
public void add(E e) {
//1.1先判断数组是否已满
if(index == objects.length){
Object [] newObjects = new Object;
System.arraycopy(objects, 0, newObjects, 0, objects.length);
objects = newObjects; //数组是引用数据类型
}
//1.2为新添加的元素指定下标
objects = e;
//1.3index自加1，以方便返回集合在大小
index++;
}
//2.根据下标访问元素
@Override
//3.返回集合大小
public int size() {
return index;
}
@Override
public Iterator iterator() {
return new ArrayListIterator();
}
private class ArrayListIterator implements Iterator {
private int currentIndex = 0;
@Override
public Object next() {
// 返回最下一个元素
Object o = objects;
currentIndex++;
return o;
}
@Override
public boolean hasNext() {
// 判断是否为最后一个元素
if(currentIndex >= index){
return false;
}
return true;
}
}
}3.LinkedList.java<span style="font-size: 16px;">public class LinkedList<E> implements Collection<E> {
private Node head;
private Node tail;
private int size;
public void add(E e){
Node n = new Node(e, null);
if(head == null){
head = n;
tail = n;
size++;
} else {
tail.setNext(n);
tail = n;
size++;
}
}
public int size(){
return size;
}
@Override
public Iterator iterator() {
return new LinkedListIterator();
}
private class LinkedListIterator implements Iterator {
private Node currentNode = head;
@Override
public Object next() {
Object o = currentNode.getData();
currentNode = currentNode.getNext();
return o;
}
@Override
public boolean hasNext() {
if(currentNode.getNext() == null){
return false;
}
return true;
}
}
}
</span>4.Node.javapublic class Node {
private Object data;
private Node next;
public Node(Object data, Node next) {
super();
this.data = data;
this.next = next;
}
public Object getData() {
return data;
}
public void setData(Object data) {
this.data = data;
}
public Node getNext() {
return next;
}
public void setNext(Node next) {
this.next = next;
}
}5.Iterator.javapublic interface Iterator {
public Object next();
public boolean hasNext();
}6.Dog.javapublic class Dog {
private int id;
public Dog(int id) {
super();
this.id = id;
}
@Override
public String toString() {
return "Dog"+id;
}
}7.测试类CollectionTest.javapublic class CollectionTest {
@Test
public void test() {
Collection co = new LinkedList();
for(int i = 0 ;i < 15 ;i++){
co.add(new Dog(i));
}
System.out.println(co.size());
Iterator it = co.iterator();
while(it.hasNext()){
System.out.println(it.next());
}
}
}运行结果
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