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/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
 
 
 class MyBasicOperations {
 
    public static void main(String a[]){
        HashMap<Person, String> hm = new HashMap<Person, String>();
        //add key-value pair to TreeMap
        Person key1= new Person();
        Person key2= new Person();
        Person key3= new Person();
        hm.put(key1, "FIRST INSERTED");
        hm.put(key2, "SECOND INSERTED");
        hm.put(key3,"THIRD INSERTED");
        System.out.println("Size of the TreeMap: "+hm.size());
        //System.out.println(hm);
        //getting value for the given key from TreeMap
        //System.out.println("Value of second: "+hm.get());
        System.out.println("Is TreeMap empty? "+hm.isEmpty());
        hm.remove(key1);
       // System.out.println(hm);
        System.out.println("Size of the TreeMap: "+hm.size());
    }
}
class Person{
	int a;
	Person(int a){
		this.a=a;
	}
}

Main.java:14: error: constructor Person in class Person cannot be applied to given types;
        Person key1= new Person();
                     ^
  required: int
  found: no arguments
  reason: actual and formal argument lists differ in length
Main.java:15: error: constructor Person in class Person cannot be applied to given types;
        Person key2= new Person();
                     ^
  required: int
  found: no arguments
  reason: actual and formal argument lists differ in length
Main.java:16: error: constructor Person in class Person cannot be applied to given types;
        Person key3= new Person();
                     ^
  required: int
  found: no arguments
  reason: actual and formal argument lists differ in length
3 errors

Standard output is empty