(必须会)经常用的List和Map在代码中常用的

Map

package com.company;

import java.util.HashMap;
import java.util.Map;

/**
 * Created by ttc on 2018/1/10.
 */
public class MapReview {
    public static void main(String[] args) {
        //创建map对象
        //key-value
        Map<String,String> words = new HashMap<>();

        //增删改查
        //增

        words.put("dog","狗");//2个参数,第一个是key,第二个是value
        words.put("cat","猫");

        //遍历map
        for(String key : words.keySet())
        {
            System.out.println(key + "----" + words.get(key));
        }

        //删
        String str = words.remove("dog");
        System.out.println(str + "被删除了");

        //遍历map
        for(String key : words.keySet())
        {
            System.out.println(key + "----" + words.get(key));
        }

        //改
        words.put("cat","小猫");
        //遍历map
        for(String key : words.keySet())
        {
            System.out.println(key + "----" + words.get(key));
        }

        //判断map中是否包含某个key
        if(words.containsKey("cat"))
        {
            System.out.println("包含猫");
        }
        else
        {
            System.out.println("不包含猫");
        }

        //遍历map的第2种方法
        for(Map.Entry entry : words.entrySet())
        {
            System.out.println(entry.getKey() + "----" + entry.getValue());
        }

    }
}

List独立

package collection;

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

/**
 * 集合里放字符串
 */
public class ListDemo
{
    public static void main(String[] args)
    {
        //List是个接口,定义实现这个接口的类ArrayList
        List<String> listDog=new ArrayList();
        Scanner scanner=new Scanner(System.in);
        while (true)
        {
            String dogName=scanner.next();
            if (dogName.equals("no"))
            {
                break;
            }
            if(!listDog.contains("ergouzi"))
            {
                listDog.add(dogName);
            }
            //listDog.add(dogName);
            //listDog.contain()   ;    listDog.remove(1), listDog.remove("abc")
        }
        listDog.remove(1);
//        for(int i=0;i<listDog.size();i++)
//        {
//            System.out.println(listDog.get(i));
//        }
        //也可以用增强for循环
            for(String dogName1:listDog)
            {
                System.out.println(dogName1);
            }

    }
}

--------------------------------------------------------

ArrayList

package array;
import java.util.ArrayList;
import java.util.List;

public class ListReview {
    public static void main(String[] args) {

        List<String> stringList = new ArrayList<>();
        stringList.add("zs");
        stringList.add("ls");
        stringList.remove("ls");
        if (stringList.contains("zs")) {
            System.out.println("yes");
        } else {
            System.out.println("no");
        }
        stringList.set(0, "ww");
        stringList.add("ww");
        for (String string : stringList) {
            System.out.println(string);
        }
    }
}

MapReview

public class MapReview {
    public static void main(String[] args) {
        Map<String ,String>words =new HashMap<>();
        words.put("dog","狗 ");
        words.put("cat","猫");
      String str =  words.remove("dog" );
        System.out.println(str+"666");

        words.put("cat","小猫");

        for (String key:words.keySet())
        {
            System.out.println(key+"----"+words.get(key));
        }

        if (words.containsKey("cat"))
        {
            System.out.println("包含");
        }
        else {
            System.out.println("不包含");
        }

        for (Map.Entry entry:words.entrySet())
        {
            System.out.println(entry.getKey()+"----"+entry.getValue());
        }
    }
}
最后编辑于
©著作权归作者所有,转载或内容合作请联系作者
平台声明:文章内容(如有图片或视频亦包括在内)由作者上传并发布,文章内容仅代表作者本人观点,简书系信息发布平台,仅提供信息存储服务。

推荐阅读更多精彩内容