hashMap分别获取所有key和value

一直记不住，这次必须得自己记录一下了，遇到就查，太浪费时间了....虽然真的很基础的问题....

1、code实现：

import java.util.*;

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);

//获取所有key
Set<Integer> keys=map.keySet();
Iterator<Integer> iterator1=keys.iterator();
while (iterator1.hasNext()){
System.out.print(iterator1.next() +", ");
}
System.out.println();
System.out.println("------------------------");

//获取所有value
Collection<Integer> values=map.values();
Iterator<Integer> iterator2=values.iterator();
while (iterator2.hasNext()){
System.out.print(iterator2.next()+", ");
}
System.out.println();
System.out.println("------------------------");

//去除value中重复值,相同值仅仅保留一个
Set<Integer> valuesSimple=new HashSet<Integer>();
for(int i:values){
valuesSimple.add(i);
}
Iterator<Integer> iterator3=valuesSimple.iterator();
while (iterator3.hasNext()){
System.out.print(iterator3.next()+", ");
}
}
}



2、输出结果：
1, 2, 3, 4,
------------------------
2, 3, 4, 4,
------------------------
2, 3, 4,
Process finished with exit code 0