HashMap中的Entry接口

利用Entry接口，快速又方便

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

public class MapDemo {
    public static void main(String[] args) {
        HashMap<Integer, String> map = new HashMap<Integer, String>();
        map.put(1,"one");
        map.put(2,"two");
        map.put(3,"three");
        for(Map.Entry<Integer, String> entry: map.entrySet()){
            System.out.println(entry.getKey() + "---" + entry.getValue());
        }
        
        //以上的foreach类似下面这个
        int[] num = new int[3];
        for (int i = 0; i < 3; i++) {
            num[i] = i;
        }
        for (int i : num){
            System.out.println(i);
        }
    }
}