What is wrong with my code?

Question about the task

Only for the rich

Java Syntax, Level 8, Lesson 8

Resolved

Hi, guys! Something is wrong with my code! Please, help me! Thank you in advance!

package com.codegym.task.task08.task0818;

import java.util.HashMap;
import java.util.Map;

/*
Only for the rich

*/

public class Solution {
    public static HashMap<String, Integer> createMap() {
        //write your code here
        HashMap<String, Integer> list = new HashMap<String, Integer>();
        list.put("Cristi1", 100);
        list.put("Cristi2", 200);
        list.put("Cristi3", 300);
        list.put("Cristi4", 400);
        list.put("Cristi5", 500);
        list.put("Cristi6", 600);
        list.put("Cristi7", 700);
        list.put("Cristi8", 800);
        list.put("Cristi9", 900);
        list.put("Cristi10", 1000);
        return list;
    }

    public static void removeItemFromMap(HashMap<String, Integer> map) {
        //write your code here

        for (Map.Entry<String, Integer> pair : map.entrySet()) {
            //System.out.println(pair.getKey() + " - " + pair.getValue());
            if (pair.getValue() < 500) {
                map.remove(pair.getKey());
            }
        }
    }

    public static void main(String[] args) {

    }
}

Create a Map<String, Integer> and add ten entries that represent (last name, salary) pairs.
Remove from the map all people whose salary is below 500.

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, Integer) elements and contains 10 entries that represent (last name, salary) pairs.
The removeItemFromMap() method must remove from the map all people whose salary is below 500.

package com.codegym.task.task08.task0818; import java.util.HashMap; import java.util.Map; /* Only for the rich */ public class Solution { public static HashMap<String, Integer> createMap() { //write your code here HashMap<String, Integer> list = new HashMap<String, Integer>(); list.put("Cristi1", 100); list.put("Cristi2", 200); list.put("Cristi3", 300); list.put("Cristi4", 400); list.put("Cristi5", 500); list.put("Cristi6", 600); list.put("Cristi7", 700); list.put("Cristi8", 800); list.put("Cristi9", 900); list.put("Cristi10", 1000); return list; } public static void removeItemFromMap(HashMap<String, Integer> map) { //write your code here for (Map.Entry<String, Integer> pair : map.entrySet()) { //System.out.println(pair.getKey() + " - " + pair.getValue()); if (pair.getValue() < 500) { map.remove(pair.getKey()); } } } public static void main(String[] args) { } }

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Onyejeme Emmanuel

Level 14

25 December 2020, 17:42

Hint: You cannot remove an item from a collection while iterating through them at the same time, thats why Java provided us with the Iterator Class. Incase you don't like the iterator Class, You can also create a copy of the map and work with it i.e. //method declaration public static void removeItemFromMap(HashMap<String, Integer> givenMap){ //a copy of the map is created HashMap<String, Integer> copyMap = new HashMap<String, Integer>(givenMap); //iterating through the copyMap for (Map.Entry pair : copyMap.entrySet()){ //the pair.getValue is of type Object, so it is //converted to string first, then to an integer if (Integer.parseInt(pair.getValue.toString()) < 500) { //you can see I remove item from //parameter given not the copyMap givenMap.remove(pair.getKey()); } } }

Vitalina

Level 20 , Poland

14 December 2020, 14:52

solution

You can remove a key from a hashmap only while Iterating. Here you have example how to remove a value from HashMap while Iterating: Iterator<Map.Entry<String, Integer>> iterator = map.entrySet().iterator(); while(iterator.hasNext()){ Map.Entry<String, Integer> pair = iterator.next(); if (pair.getValue() < 500) { iterator.remove(); } If you want to check if the code is working - just print this code in main method: HashMap<String, Integer> map = createMap(); for(Map.Entry<String, Integer> pair : map.entrySet()){ System.out.println(pair.getKey() + " : " + pair.getValue()); } System.out.println("____________________________"); removeItemFromMap(map); for(Map.Entry<String, Integer> pair : map.entrySet()){ System.out.println(pair.getKey() + " : " + pair.getValue()); } Let me know if you need some extra explanation:)