for (String name : likedBy) { String likedUser= name.trim(); Set likes = likesMap.getOrDefault(likedUser, new HashSet<>()); Here you create a new Set for likes. This is in the iteration over the likers though so it results in many missing entries. [ How do i Fix this ] import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; import java.util.ArrayList; import java.util.HashMap; import java.util.HashSet; import java.util.List; import java.util.Map; import java.util.Set; public class FacebookLikeManager { private Map> likesMap; public FacebookLikeManager() { likesMap = new HashMap<>(); } public void buildMap(String filePath) { try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) { String line = reader.readLine(); while (line != null) { String[] lineWords = line.split(":"); String user = lineWords[0].trim(); String[] likedBy = lineWords[1].split(","); for (String name : likedBy) { String likedUser= name.trim(); Set likes = likesMap.getOrDefault(likedUser, new HashSet<>()); likes.add(user); likesMap.put(likedUser, likes); } line = reader.readLine(); } } catch (IOException ex) { System.err.format("IOException: %s%n", ex); } } public List getAllUsers() { return new ArrayList<>(likesMap.keySet()); } public List getLikes(String user) { Set liked = likesMap.get(user); if (liked == null) { liked = new HashSet<>(); } return new ArrayList<>(liked); } public List getLikedBy(String user) { List likedBy = new ArrayList<>(); for (Map.Entry> post : likesMap.entrySet()) {

for (String name : likedBy) { String likedUser= name.trim(); Set likes = likesMap.getOrDefault(likedUser, new HashSet<>()); Here you create a new Set for likes. This is in the iteration over the likers though so it results in many missing entries. [ How do i Fix this ] import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; import java.util.ArrayList; import java.util.HashMap; import java.util.HashSet; import java.util.List; import java.util.Map; import java.util.Set; public class FacebookLikeManager { private Map> likesMap; public FacebookLikeManager() { likesMap = new HashMap<>(); } public void buildMap(String filePath) { try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) { String line = reader.readLine(); while (line != null) { String[] lineWords = line.split(":"); String user = lineWords[0].trim(); String[] likedBy = lineWords[1].split(","); for (String name : likedBy) { String likedUser= name.trim(); Set likes = likesMap.getOrDefault(likedUser, new HashSet<>()); likes.add(user); likesMap.put(likedUser, likes); } line = reader.readLine(); } } catch (IOException ex) { System.err.format("IOException: %s%n", ex); } } public List getAllUsers() { return new ArrayList<>(likesMap.keySet()); } public List getLikes(String user) { Set liked = likesMap.get(user); if (liked == null) { liked = new HashSet<>(); } return new ArrayList<>(liked); } public List getLikedBy(String user) { List likedBy = new ArrayList<>(); for (Map.Entry> post : likesMap.entrySet()) {

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Related questions

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Question

for (String name : likedBy) {

String likedUser= name.trim();
Set<String> likes = likesMap.getOrDefault(likedUser, new HashSet<>());

Here you create a new Set for likes. This is in the iteration over the likers though so it results in many missing entries. [ How do i Fix this ]

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.HashSet;

import java.util.List;

import java.util.Map;

import java.util.Set;

public class FacebookLikeManager {

private Map<String, Set<String>> likesMap;

public FacebookLikeManager() {

likesMap = new HashMap<>();

}

public void buildMap(String filePath) {

try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {

String line = reader.readLine();

while (line != null) {

String[] lineWords = line.split(":");

String user = lineWords[0].trim();

String[] likedBy = lineWords[1].split(",");

for (String name : likedBy) {

String likedUser= name.trim();

Set<String> likes = likesMap.getOrDefault(likedUser, new HashSet<>());

likes.add(user);

likesMap.put(likedUser, likes);

}

line = reader.readLine();

}

} catch (IOException ex) {

System.err.format("IOException: %s%n", ex);

}

public List<String> getAllUsers() {

return new ArrayList<>(likesMap.keySet());

}

public List<String> getLikes(String user) {

Set<String> liked = likesMap.get(user);

if (liked == null) {

liked = new HashSet<>();

}

return new ArrayList<>(liked);

}

public List<String> getLikedBy(String user) {

List<String> likedBy = new ArrayList<>();

for (Map.Entry<String, Set<String>> post : likesMap.entrySet()) {

if (post.getValue().contains(user)) {

likedBy.add(post.getKey());

}

return likedBy;

}

public class Main {

public static void main(String[] args) {

FacebookLikeManager main = new FacebookLikeManager();

main.buildMap(args[0]);

System.out.println(main.getAllUsers());

System.out.println(main.getLikes("Kristen"));

System.out.println(main.getLikedBy("Sara"));

}

Mike: Kristen, Sara, Nate, Anthony, Randy
Kristen: Mike, John, Steve, Bill
Bill: Sara, Nate
Sara: Nate, Anthony

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