Cant solve the task.

Question about the task

We don't need repeats

Java Syntax, Level 8, Lesson 8

Under discussion

Please help me with my code.It is not satisfying 4th condition.What's the error?

Create a Map<String, String> and add ten entries that represent (last name, first name) pairs.
Remove people with the same first name.

Requirements:

The program should not display text on the screen.
The program should not read values from the keyboard.
The createMap() method must create and return a HashMap that has (String, String) elements and contains 10 entries.
The removeFirstNameDuplicates() method must remove from the map all people who have the same first name.
The removeFirstNameDuplicates() method must call the removeItemFromMapByValue() method.

package com.codegym.task.task08.task0817; import java.util.HashMap; import java.util.Map; import java.util.Iterator; /* We don't need repeats */ public class Solution { public static HashMap<String, String> createMap() { HashMap <String,String> a= new HashMap<String,String>(); a.put("1","A"); a.put("2","B"); a.put("3","B"); a.put("4","c") ; a.put("5","B"); a.put("6","B"); a.put("7","B") ; a.put("8","B") ; a.put("9","B") ; a.put("10","e");//write your code here // removeFirstNameDuplicates(a); return a; } public static void removeFirstNameDuplicates(Map<String, String> map) { //String s=map.values(); //Iterator<Map.Entry<String,String>> b= a.entrySet.iterator(); HashMap <String,String> aa= new HashMap<String,String>(map); Iterator<Map.Entry<String,String>> p=aa.entrySet().iterator(); while(p.hasNext()){ Map.Entry<String,String> c=p.next(); String z= c.getValue(); removeItemFromMapByValue(map,z); //write your code here } } public static void removeItemFromMapByValue(Map<String, String> map, String value) { HashMap<String, String> copy = new HashMap<String, String>(map); for (Map.Entry<String, String> pair : copy.entrySet()) { if (pair.getValue().equals(value)) map.remove(pair.getKey()); } } public static void main(String[] args) { } }

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Sela

Level 20 , Poland

2 July 2020, 13:17

Gellert Varga is right. one of possible solutions is to: 1. create an Array and fill it with all the entry values (not keys) copied from the map 2. create an ArrayList for duplicates 3. any duplicates found in the Array add into ArrayList 4. and finally remove all the map entries if the entry value is equal to duplicate element

Gellert Varga

Level 23 , Szekesfehervar, Hungary

9 May 2020, 22:52

If you paste this code into main() for testing and run the program, you will see what your program does:

Map<String,String> names = createMap();
     System.out.println(names);
     System.out.println(names.size());

removeFirstNameDuplicates(names);
     System.out.println(names);
     System.out.println(names.size());

Your removeFirstNameDuplicates() method iterates all the pairs throughout, gets its value, and without any condition passes them one by one to the removeItemFromMapByValue() method for deletion. So we end up deleting all the items from the map. You need to do some checking/comparisions during iteration for purpose to pass only the duplicated names to the removeDuplicates() method.