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Start your free trialKyler Callaway
6,257 PointsHow do I solve this?
I am new to the Maps Interface and generics in general can someone please explain this to me ?
package com.example;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
public class BlogPost implements Comparable<BlogPost>, Serializable {
private String mAuthor;
private String mTitle;
private String mBody;
private String mCategory;
private Date mCreationDate;
public BlogPost(String author, String title, String body, String category, Date creationDate) {
mAuthor = author;
mTitle = title;
mBody = body;
mCategory = category;
mCreationDate = creationDate;
}
public int compareTo(BlogPost other) {
if (equals(other)) {
return 0;
}
return mCreationDate.compareTo(other.mCreationDate);
}
public String[] getWords() {
return mBody.split("\\s+");
}
public List<String> getExternalLinks() {
List<String> links = new ArrayList<String>();
for (String word : getWords()) {
if (word.startsWith("http")) {
links.add(word);
}
}
return links;
}
public String getAuthor() {
return mAuthor;
}
public String getTitle() {
return mTitle;
}
public String getBody() {
return mBody;
}
public String getCategory() {
return mCategory;
}
public Date getCreationDate() {
return mCreationDate;
}
}
package com.example;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class Blog {
List<BlogPost> mPosts;
public Blog(List<BlogPost> posts) {
mPosts = posts;
}
public List<BlogPost> getPosts() {
return mPosts;
}
public Set<String> getAllAuthors() {
Set<String> authors = new TreeSet<>();
for (BlogPost post: mPosts) {
authors.add(post.getAuthor());
}
return authors;
}
public Map<String> getCategoryCount<String>(){
Map<String,Integer> CategoryCount = new HashMap<String,Integer>();
for(BlogPost blog : mPosts){
Integer counts = CategoryCounts.get(blog);
if(count ==null){
count =0;
}
count++;
getCategoryConts.put(blog,counts);
}
return CategoryCount;
}
}
2 Answers
jcorum
71,830 PointsGrigorij has covered it well! But if you want another take on it here's a link to a slightly different line-by-line explanation: https://teamtreehouse.com/community/java-help-7
Grigorij Schleifer
10,365 PointsHey Kyler,
you are very close:
public Map<String, Integer> getCategoryCounts() { // <String> deleted, <Integer> added
Map<String, Integer> CategoryCount = new HashMap<String, Integer>();
for (BlogPost blog : mPosts){
Integer count = CategoryCount.get(blog.getCategory());
// specify what you need from the "blog" using getCategory() method
// count the returned categories
if (count == null){
count = 0;
// if no category yet, getCategory() will return null
// set the count to 0 if no categories yet
}
count ++;
// increase the count if Category is found
CategoryCounts.put(blog.getCategory(), count);
// put the caregory as key and the number as value into the Map
}
return CategoryCounts;
// and return it
}
Makes sense?
Grigorij
Grigorij Schleifer
10,365 PointsGrigorij Schleifer
10,365 PointsHey jcorum you are absolutely right !
Ken Alger for president !!!
Oh no I forget, Craig is already nominated :)))