Java集合

集合

• 集合框架体系

Collection 接口有两个只要的孩子接口 List Set，他们的实现子类都是单列集合

• Collection
  • List
    • ArrayList（线程不安全）
    • LinkedList
    • Vector
  • Set
    • HashSet
    • LinkedHashSet
    • TreeSet

Map 接口的实现子类 是双列集合，存放的K-V

• Map
  • HashMap
    • LinkedHashMap
  • Hashtable
    • Properties
  • TreeMap
• Collection

public class Application {
    public static void main(String[] args) {
        //add:添加单个元素
        ArrayList List = new ArrayList();
        List.add("马青松");
        List.add("mqs");
        System.out.println(List);
        //remove:删除指定元素
        List.remove(1);
        System.out.println(List);
        //contains:查找元素是否存在
        System.out.println(List.contains("马青松"));
        //size:获取元素个数
        System.out.println(List.size());
        //isEmpty:判断元素个数
        System.out.println(List.isEmpty());
        //clear:清空
        List.clear();
        System.out.println(List);
        //addAll:添加多个元素
        ArrayList List2 = new ArrayList();
        List2.add("马青松");
        List2.add("目前是");
        List.addAll(List2);
        System.out.println(List);
        //containsAll:查找多个元素是否都存在
        System.out.println(List.containsAll(List2));
        //removeAll:删除多个元素
        List.removeAll(List2);
        System.out.println(List);

    }
}

迭代器遍历

public class Application {
    public static void main(String[] args) {
        Collection col = new ArrayList();
        col.add(new Book("三国演义","罗贯中",10.1));
        col.add(new Book("红楼梦","蓝屏",10.1));
        col.add(new Book("小李飞刀","路旁",10.1));

        //System.out.println("col=" +col);
        //现在希望能够遍历 col集合
        //1.先得到col对应的迭代器
        Iterator iterator = col.iterator();
        //2.使用while循环遍历
        while (iterator.hasNext()){//判断是否还有数据
            Object obj = iterator.next();
            System.out.println(obj);
        }
    }
}

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 +
                '}';
    }
}

List接口方法：

public class Application {
    public static void main(String[] args) {
        //List集合类中元素有序（即添加顺序和取出顺序一致），且可重复
        List list = new ArrayList();
        list.add("jake");
        list.add("tom");
        list.add("mqs");
        list.add("kojds");
        list.add("jake");
        System.out.println(list);
        //List集合中的每个元素都有其对应的顺序索引，即支持索引
        System.out.println(list.get(2));
    }
}

List底层源码

 List接口联系：

public class Application {
    @SuppressWarnings({"all"})
    public static void main(String[] args) {
       List list = new ArrayList();
       list.add(new Book("西游记","mqs",20.00));
       list.add(new Book("阿衰梦","mqs",40.00));
       list.add(new Book("红楼梦","mqs",10.00));
       list.add(new Book("马青松","mqs",70.00));
        sort(list);
        for (Object o:list){
            System.out.println(o);
        }
    }

    public static void sort( List list){
        for (int i=0; i<list.size()-1; i++){
            for (int j=0; j<list.size()-1-i; j++){
               Book book1 = (Book)list.get(j);
                Book book2 = (Book)list.get(j+1);
                if (book1.getPrice()  > book2.getPrice()){
                        list.set(j,book2);
                        list.set(j+1,book1);
                }
            }
        }
    }

    public static 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  name + '/t' + author + '/t'+ price + '/t';
        }
    }
}

LinkedList的底层实现了双向链表和双端队列特点

可以添加任意元素（元素可以重复）包括null

线程不安全，没事实现同步

LinkedList底层源码

public class Application {
    @SuppressWarnings({"all"})
    public static void main(String[] args) {
        LinkedList linkedList = new LinkedList();
        linkedList.add("MQS");

        System.out.println(linkedList);
        System.out.println(linkedList.get(0));
        System.out.println(linkedList.indexOf("MQS"));
        //ArrayList方法都有
    }
}