Collection接口继承了Iterable接口，List接口和Set接口继承了Collection接口，Vector ArrayList LinkedList 类实现了List接口，TreeSet 类和HashSet类实现了Set接口。（Vector ArrayList LinkedList 类称为List接口的实现子类）
Collection 接口有两个重要的子接口List Set ,他们的实现子类都是单列集合

. Map接口的实现子类是双列集合，存放的K-V

1.3.1Collection接口和常用方法

public interface Collection <E> extends iterable<E>

collection的实现子类可以存放多个元素,每个元素可以是object
有些collection的实现类,可以存放重复的元素,有些不可以
有些collection的实现类是有序的(List),有些是无序的(Set)
Collection接口没有直接实现的子类,是通过他的接口List 和 Set 来实现的

1.3.2Collection接口常用方法,以实现子类ArrayList来演示. CollectionMethod.java

package com.cds.CollectionMethod;

import java.util.ArrayList;
import java.util.List;

public class CollectionMethod {
    public static void main(String[] args) {
        List list = new ArrayList();
        list.add("jack");//添加元素
        list.add(10);//这里存在将int类型转换成Integer
        System.out.println("list=" + list);
        System.out.println(list.contains("jack"));//返回Boolean
        System.out.println(list.size());//得到集合的大小
        System.out.println(list.isEmpty());//判断是否为空
//        list.remove(0);//删除第0个元素
//        list.remove(jcak);//删除指定元素
//        list.clear();//清空
//        System.out.println(list);
        ArrayList list2 = new ArrayList();
        list2.add("刘小美");
        list2.add(0,"张晓梅");
        System.out.println("===========");
        System.out.println("list2= "+list2);
        list.addAll(list2);//添加多个元素
        System.out.println("list="+list);
        System.out.println(list.containsAll(list2));
        list2.add(0,"柴东升");
        System.out.println("list="+list);
        System.out.println("list2="+list2);
    }
}

1.4.1 Collection接口遍历元素方式1-使用Iterator(迭代器)

Iterator对象称为迭代器,主要用于遍历Collection集合中的元素
所有实现了Collection接口的集合类都有一个Iterator()方法

Iterator仅仅用于遍历集合,Iterator本身并不存放对象

1.4.2迭代器的执行原理(看代码,含详细解释)

package com.cds.collectionIterator;

import java.util.ArrayList;
import java.util.Iterator;

public class CollectionIterator01 {
    public static void main(String[] args) {
        @SuppressWarnings({"all"})
        ArrayList arrayList = new ArrayList();
        arrayList.add(new Book("平凡的世界","路遥",30.5));
        arrayList.add(new Book("白鹿原","陈忠实",60.0));
        arrayList.add(new Book("告白与告别","韩寒",45.5));
        arrayList.add(18);
        Iterator iterator = arrayList.iterator();//得到arrayList的迭代器
        while(iterator.hasNext()){//hasNext()判断是否还有下一个元素
            Object obj = iterator.next();//1、下移2、将 下面的集合位置上元素返回
            System.out.println(obj );
        }
        iterator = arrayList.iterator();//重置迭代器
        System.out.println(iterator.hasNext());
        for (Object book:arrayList){
            System.out.println("book="+book);
        }



//        while (iterator.hasNext()) {
//            Object next =  iterator.next();
//
//        }
    }
}
class Book{
     private String name;
     private String author;
     private double price;

    public Book(String name, String author, double price) {
        this.name = name;
        this.author = author;
        this.price = price;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    @Override
    public String toString() {
        return "Book{" +
                "name='" + name + '\'' +
                ", author='" + author + '\'' +
                ", price=" + price +
                '}';
    }
}