HashMap obtains all keys and values respectively

I can't remember. I have to record it myself this time. I'll check it if I encounter it. It's a waste of time Although it's really a basic problem

1. Code implementation:

public class Main {

public static void main(String[] args){

//        Scanner scanner=new Scanner(system.in);//在线笔试

HashMap<Integer,Integer> map=new HashMap<Integer,Integer>();

map.put(1,2);

map.put(2,3);

map.put(3,4);

map.put(4,4);

    //<a href="https://www.jb51.cc/tag/huoqu/" target="_blank" class="keywords">获取</a>所有key
    Set<Integer> keys=map.keySet();
    Iterator<Integer> iterator1=keys.iterator();
    while (iterator1.hasNext()){
        Sy<a href="https://www.jb51.cc/tag/stem/" target="_blank" class="keywords">stem</a>.out.print(iterator1.next() +",");
    }
    Sy<a href="https://www.jb51.cc/tag/stem/" target="_blank" class="keywords">stem</a>.out.println();
    Sy<a href="https://www.jb51.cc/tag/stem/" target="_blank" class="keywords">stem</a>.out.println("------------------------");

    //<a href="https://www.jb51.cc/tag/huoqu/" target="_blank" class="keywords">获取</a>所有value
    Collection<Integer> values=map.values();
    Iterator<Integer> iterator2=values.iterator();
    while (iterator2.hasNext()){
        Sy<a href="https://www.jb51.cc/tag/stem/" target="_blank" class="keywords">stem</a>.out.print(iterator2.next()+",");
    }
    Sy<a href="https://www.jb51.cc/tag/stem/" target="_blank" class="keywords">stem</a>.out.println();
    Sy<a href="https://www.jb51.cc/tag/stem/" target="_blank" class="keywords">stem</a>.out.println("------------------------");

    //<a href="https://www.jb51.cc/tag/quchu/" target="_blank" class="keywords">去除</a>value中重复值,相同值仅仅保留<a href="https://www.jb51.cc/tag/yige/" target="_blank" class="keywords">一个</a>
    Set<Integer> valuesSimple=new HashSet<Integer>();
    for(int i:values){
        valuesSimple.add(i);
    }
    Iterator<Integer> iterator3=valuesSimple.iterator();
    while (iterator3.hasNext()){
        Sy<a href="https://www.jb51.cc/tag/stem/" target="_blank" class="keywords">stem</a>.out.print(iterator3.next()+",");
    }
}
}



2. Output results: