Grundlegende Methode zum Durchlaufen von HashMap

package mAp;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

public class TestMap {
    
    
    public static void main(String[] args) {
    
    
        Map<Integer,String> map=new HashMap<>();
        map.put(1,"China");
        map.put(2,"India");
        map.put(3,"USA");
        map.remove(3);
        map.put(4,"Canada");
        //利用for
        Set<Integer> keys=map.keySet();
        System.out.print("这是for:"+'\n');
        for(Integer key:keys) {
    
    
            String value=map.get(key);
            System.out.println("key:"+key+" and  value :"+value);
        }
        //使用entry
        System.out.print("这是entry:"+'\n');
        Set<Map.Entry<Integer,String>> entries=map.entrySet();
        for(Map.Entry<Integer,String> entry:entries) {
    
    
            Integer key =entry.getKey();
            String value=entry.getValue();
            System.out.println("key:"+key+"  and  value:"+value);
        }
        //Iterator
        System.out.print("这是Iterator:"+'\n');
        Set<Integer> keySet = map.keySet();
        Iterator<Integer> iterator=keySet.iterator();
        while(iterator.hasNext()) {
    
    
            Integer key= iterator.next();
            System.out.println("key:"+key+" and value :"+map.get(key));
            
        }
    }


}