Still struggling with this one

Question about the task

We don't need repeats

Java Syntax, Level 8, Lesson 8

Under discussion

Can anybody please explain how this works. Very much appreciated!

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.*; /* We don't need repeats */ public class Solution { public static HashMap<String, String> createMap() { //write your code here HashMap<String, String> map = new HashMap<>(); map.put("LastName1", "Name1");//create a HashMap with 10 key-value pairs (lastName , name) map.put("LastName2", "Name1");//changed the first letter to capitals map.put("LastName3", "Name5");//changed the name of the HashMap from names to map map.put("LastName4", "Name7");//still not working why? map.put("LastName5", "Name9");// keys CANNOT be the same map.put("LastName6", "Name10");//values can be the same but NOT the keys map.put("LastName7", "Name11"); map.put("LastName8", "Name13"); map.put("LastName9", "Name14"); map.put("LastName10", "Name15"); return map; } public static void removeFirstNameDuplicates(Map<String, String> map) {// should this not be HashMap instead of Map? //write your code here Iterator<Map.Entry<String, String>> iterator = map.entrySet().iterator();//create an iterator for(Map.Entry<String, String> entry: map.entrySet())//loop over all the pairs in map { while(iterator.hasNext())// check is there is a next element int list { Map.Entry<String, String> pair = iterator.next();//gives next element String value = pair.get(key); //get the value of this pair if(pair.getValue().equals(value)){//to compare the value with next value removeItemFromMapByValue();// this should call the method to remove this element. } } } } 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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- FniJnn -

Level 33 , Paris, France

18 February 2020, 20:57

Try this

for(Map.Entry<String, String> pair: map.entrySet())//loop over all the pairs in map
        {
                String value = pair.getKey(); //get the value of this pair
                if(pair.getValue().equals(value)){//to compare the value with next value
                    removeItemFromMapByValue(map, value);// this  should call the method to remove this element.
            }
        }

MaGaby2280

Level 41 , Guatemala City, Guatemala

17 February 2020, 16:55

You have to put your 10 elements in a Hashmap, not in map, and return a hashmap. //hashmap.put(String,String); In your code you are puting them in a map and returning a map, not a hashmap.

Liliane Top

Level 17 , Amsterdam, Netherlands

17 February 2020, 17:05

Thanks for responding appreaciate it. But what is the difference between a hashmap and map in this case?

Liliane Top

Level 17 , Amsterdam, Netherlands

17 February 2020, 17:07

so it should be like this: public static void removeFirstNameDuplicates(HashMap<String, String> map)

MaGaby2280

Level 41 , Guatemala City, Guatemala

17 February 2020, 17:16

useful

In this case, the instructions tell you to use a HashMap, so in order to pass the requirements you must use a Hashmap. The differencce is that a Map is an interface that HashMap implements. A Map is an interface,that defines how something can be used. HashMap is an implementation of that interface.

Liliane Top

Level 17 , Amsterdam, Netherlands

17 February 2020, 17:33

Okay I get it! Thanks. I changed it and I do get less errors but still stuck on that it doesn't recognize the bit about the following: error: cannot find symbol if(map.getValue().equals(value)){//to compare the value with next value?? ^