how i can remove duplicates first name..???

Question about the task

We don't need repeats

Java Syntax, Level 8, Lesson 8

Resolved

any specific method t compare values of map please help

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.*; /* 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("1", "farhan"); map.put("2", "sahar"); map.put("3", "farah"); map.put("4", "sahar"); map.put("5", "saba"); map.put("6", "kiran"); map.put("7", "tayyab"); map.put("8", "sarwar"); map.put("9", "masood"); map.put("10", "parha"); return map; } public static void removeFirstNameDuplicates(Map<String, String> map) { //write your code here int count = 0; for (Map.Entry<String, String> t : map.entrySet()) { String s0 = t.getValue(); for (Map.Entry<String, String> s : map.entrySet()) { String s1 = s.getValue(); if (s0.equals(s1)) { removeItemFromMapByValue(map,s1); count = 1; } if(count ==1) { removeItemFromMapByValue(map,s0); } count = 0; } } } 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 { HashMap<String,String> map = new HashMap<>(); map = createMap(); System.out.print(map); } }

Comments (3)

Popular
New
Old

You must be signed in to leave a comment

Tayyab Mubeen

Level 16 , Lahore, Pakistan

14 October 2018, 03:40

any help..??

Ankush Rajput

Level 25 , Bhopal, India

13 October 2018, 23:58

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());
        }   }
        }

See this function. You are passing reference to map in function. Ok. In next line you are making a copy of that map and deleting elements from the copy. Since you've made changes in the copy of the map and not original map, you need to return the map and then somehow store it again in calling function. This is one option. What if you don't make a copy inside function removeItemFromMapByValue() and directly remove from the original map reference ? As we know Map do not support concurrent modification, you'll get concurrent modification exception because in removeFirstNameDuplicates() iterators is still traversing the map and you are removing from map. It won't work even if you modify your code to use iterator.remove on map in removeItemFromMapByValue(). It can be thought of as analogy - one iterator is removing without knowledge of other iterator and hence concurrent modification exception. So, what other option we have ? You can make a copy of map in removeFirstNameDuplicates function and traverse the copy using iterators and check requirements. But when passing parameters to removeItemFromMapByValue(), pass original map reference and not copy. In this way you'll be operating on two map objects without interfering with each other.

Tayyab Mubeen

Level 16 , Lahore, Pakistan

14 October 2018, 02:35

okay i understand....i did it but it still not working

public static void removeFirstNameDuplicates(Map<String, String> map) {
        //write your code here
        HashMap<String, String> temp = new HashMap<String, String>(map);

        int count = 0, no = 0;
        for (Map.Entry<String, String> t : temp.entrySet()) {
            String s0 = t.getValue();
            for (Map.Entry<String, String> s : temp.entrySet())
            {
                String s1 = s.getValue();
                if (s0.equals(s1))
                {
                    count++;
                }
                if(count > 1)
                {
                    removeItemFromMapByValue(map,s1);
                    no = 1;
                    count = 1;
                }
                if (no == 1)
                {
                    removeItemFromMapByValue(map,s0);
                }
                no = 0;
            }

        }

    }

    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());
            }
        }
    }