[数据结构与算法]Map的三种类型和map的遍历

import java.util.*;

public class mapsComparison {
    public static void main(String[] args) {
        //没有顺序
        Map<Integer,String> map=new HashMap<>();
        map.put(1,"java1班");
        map.put(2,"java2班");
        map.put(4,"java4班");
        map.put(3,"java3班");
        System.out.println("hashmap的输出结果"+map.toString());
        //按添加顺序
        Map<Integer,String> map2=new LinkedHashMap<>();
        map2.put(1,"java1班");
        map2.put(2,"java2班");
        map2.put(4,"java4班");
        map2.put(3,"java3班");
        System.out.println("linkedhashmap的输出结果"+map2.toString());
        //二叉树顺序，左小右大
        Map<String,String> map3=new TreeMap<>();
        map3.put("one","java1班");
        map3.put("two","java2班");
        map3.put("4","java4班");
        map3.put("3","java3班");
        System.out.println("treemap的输出结果"+map3.toString());
        //获取所有的key得到一个set
        Set<String> strings = map3.keySet();
        System.out.println(strings);
        //通过遍历key来得到所有的value
        for(String s:strings){
            System.out.println(map3.get(s));
        }
        

    }
}

打印的结果为：

hashmap的输出结果{1=java1班, 2=java2班, 3=java3班, 4=java4班}
linkedhashmap的输出结果{1=java1班, 2=java2班, 4=java4班, 3=java3班}
treemap的输出结果{3=java3班, 4=java4班, one=java1班, two=java2班}
keyset得到的结果为：[3, 4, one, two]
java3班
java4班
java1班
java2班