import java.util.*;
public class SetTest {
public static void main(String[] args) {
HashMap hashMap = new HashMap<>();
hashMap.put("a","1");
hashMap.put("b","2");
TreeMap treeMap = new TreeMap<>();
treeMap.put("a","1");
treeMap.put("b","2");
System.out.println(hashMap);
System.out.println(treeMap);
HashSet hashSet = new HashSet<>();
hashSet.add("a");
hashSet.add("b");
TreeSet treeSet = new TreeSet<>();
treeSet.add("a");
treeSet.add("b");
Hashtable hashtable=new Hashtable<>();
}
}