Collection.java

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;

public class Collection 
{
	static Map<String, List<String>> map1 = new HashMap<String, List<String>>();
	static Map<String,Integer> map2 = new HashMap<String,Integer>();
	public void add_in_map1(String key, List<String> values)
	{
		 map1.put(key, values);
		 System.out.println(map1);
	}
	public void delete_in_map1(String key)
	{
		 map1.remove(key);
		 System.out.println(map1);
	}

	public void findFaculties(String key)
	{
		if(map1.containsKey(key))
		{
			List<Integer> faculties = new ArrayList<Integer>();
			List<String> list = map1.get(key);
			Set<String> keys = map2.keySet();
			for(String l:list)
			{
				for(String k:keys)
				{
					if(l.equals(k))
					{
						faculties.add(map2.get(k));	
					}
				}
			}
			System.out.println(faculties);
		}
		else
			System.out.println("No such student");
	}
    public static void main(String[] args) 
    {
        
        List<String> valSetOne = new ArrayList<String>();
        valSetOne.add("Python");
        valSetOne.add("Maths");
        valSetOne.add("C");
       
        List<String> valSetTwo = new ArrayList<String>();
        valSetTwo.add("C");
        valSetTwo.add("C++");
       
        List<String> valSetThree = new ArrayList<String>();
        valSetThree.add("C++");
        valSetThree.add("Physics");
        valSetThree.add("Chemistry");
       
        map1.put("A", valSetOne);
        map1.put("B", valSetTwo);
        map1.put("C", valSetThree);

        map2.put("Python", 111);
        map2.put("Maths", 222);
        map2.put("C", 333);
        map2.put("C++", 444);
        map2.put("Physics", 555);
        map2.put("Chemistry", 666);
        
        System.out.println("Fetching Keys and corresponding [Multiple] Values:\n");
        for (Map.Entry<String, List<String>> entry1 : map1.entrySet()) 
        {
            String key1 = entry1.getKey();
            List<String> values1 = entry1.getValue();
            System.out.println("Key = " + key1);
            System.out.println("Values = " + values1);
        }
        System.out.println("Fetching Keys and corresponding [Single] Values: \n");
        for (Map.Entry<String,Integer> entry2 : map2.entrySet()) 
        {
            String key2 = entry2.getKey();
            Integer values2 = entry2.getValue();
            System.out.println("Key = " + key2);
            System.out.println("Values = " + values2);
        }
        System.out.println("enter choice:");
        {
        	Scanner sc = new Scanner(System.in);
        	int choice=sc.nextInt();
        	switch(choice)
        	{
        	case 1:
        		Collection c1 = new Collection();
                List<String> val = new ArrayList<String>();
                val.add("HPC");
                val.add("CS");
                val.add("DSA");
                c1.add_in_map1("D",val);
                break;
        	case 2:
        		Collection c2 = new Collection();
                c2.delete_in_map1("B");
                break;
        	case 3:
        		Collection c3 = new Collection();
        		c3.findFaculties("E");
        		break;
        	default:
        		System.out.println("error");
        	}
        }
    }
}