常用方法

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

public class CollectionMethod {
    public static void main(String[] args) {
        List list = new ArrayList();
        // add 添加单个元素
        list.add("jack");
        list.add(10);
        list.add(true);
        System.out.println("list="+list);

        //remove:删除指定元素
        list.remove(0);
        System.out.println("list="+list);

        //contanins:查找元素是否存在
        System.out.println(list.contains("jack"));

        //size:获取元素个数
        System.out.println(list.size());

        //isEmpty:判断是否为空
        System.out.println(list.isEmpty());

        //clear:清空
        //list.clear()

        //addAll:添加多个元素
        ArrayList list2 = new ArrayList();
        list2.add("hhh");
        list2.add("hhh");
        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.add("聊斋");
        list.removeAll(list2);
        System.out.println(list);

    }
}

Collection接口遍历元素方法

1、lterator迭代器

快捷键itit

package top.ltyzqhh.collection;

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

public class CollectionIterator {
    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("西游记","吴承恩",10.3));
        col.add(new Book("红楼梦","曹雪芹",10.5));

        //1.先得到col对于的迭代器
        Iterator iterator = col.iterator();
        //2while循环遍历
        while (iterator.hasNext()) {//判断是否还有数据
            //返回下一个元素，类型是Object
            Object next =  iterator.next();
            System.out.println("obj="+next);
        }
        //3.当退出while循环后，Iterator指向最后的元素，
        //4.如果希望再次遍历。需要重置我们的迭代器
            iterator=col.iterator();
        

    }
}

class Book{
    private String name;
    private String author;
    private double price;

    public Book() {
    }

    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 +
                '}';
    }
}

2.增强for循环

增强for循环也可用于数组,底层依然是迭代器快捷键I

package top.ltyzqhh.collection;

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

public class CollectionIterator {
    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("西游记","吴承恩",10.3));
        col.add(new Book("红楼梦","曹雪芹",10.5));

        //增强for循环
        //底层依然是迭代器
        //可以理解成简化版的迭代器
        //快捷键 I
        for (Object book:col) {
            System.out.println(book);
        }

    }
}

class Book{
    private String name;
    private String author;
    private double price;

    public Book() {
    }

    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 +
                '}';
    }
}