How is the problem solved?

Question about the task

We don't need repeats

Java Syntax, Level 8, Lesson 8

Under discussion

The removeFirstNameDuplicates() method must remove from the map all people who have the same first name.

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; public class Solution { public static HashMap<String, String> createMap() { HashMap<String, String> hashMap = new HashMap<>(); for(int i = 0; i < 10; i++) { hashMap.put("A"+i, "B"); } return hashMap; } public static void removeFirstNameDuplicates(Map<String, String> map) { HashMap<String, String> Copy = new HashMap<>(map); for (Map.Entry<String, String> pair : Copy.entrySet() ) { removeItemFromMapByValue(Copy, pair.getValue()); } } 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) throws Exception { } }

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zhaoyang

Level 25 , Los Angeles, United States

18 June 2019, 19:08

In this function removeFirstNameDuplicates, you just delete element from the copy version of input map, not the map, so actually, the input map don't change any thing. The reason of Using copy of map is to avoid errors may happen during the process of change the map elements in the for-loop. To solve problem, the hint is you may need to know which first name appear more than once, so you could use the removeItemFromMapByValue function to delete these pairs. Hope this message help you!

John Michael Montuya

Level 10 , Cebu City, Philippines

16 June 2019, 07:33

I've been stuck with that verification failure for so long until I realized that java, for some reason, does not like it when you delete elements from a map while you are iterating through that very map. What I did was create to 2 copycat hash maps (exact clone) of the actual map that you pass to the method. Now you have to iterate through both copycat sets via for:each loop and increment a variable counter every time you land a match on the map value(first name). When counter is equal to or greater than 2 (first match or counter value of 1 does not count since it's expected for clone maps), take note of the last value that you matched and remove that via the following statement (where map is the original map that you pass to the method and dupe is the duplicate value): removeItemFromMapByValue(map, dupe); I hope this helps.