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Java Java Data Structures - Retired Exploring the Java Collection Framework ArrayLists

Jack Cummins
Jack Cummins
17,417 Points
Posted by Jack Cummins
Jack Cummins
17,417 Points

Why is my answer wrong? I give out best answers if you give me a good answer.

Assignment: Let's add a method that returns a list of all links in the body of the document. All words that start with http should be considered links. Name it getExternalLinks.

NOTE: Remember to import the needed classes from java.util. HINT: We already made the getWords method, we should use it!

Thanks! Jack

com/example/BlogPost.java 
package com.example;

import java.io.Serializable;
import java.util.Date;
import java.util.ArrayList;
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 List<String> getExternalLinks (){
    List<String> results = new ArrayList<String>();

    for (String word : getWords()){
      if word.startsWith("http"){
        results.add(word)
      }
    }
  }

  public int compareTo(BlogPost other) {
    if (equals(other)) {
      return 0;
    }
    return mCreationDate.compareTo(other.mCreationDate);
  }

  public String[] getWords() {
    return mBody.split("\\s+");
  }

  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;
  }
  public getExternalLinks(){

  }
}

2 Answers

Amanda Allison
Amanda Allison
9,104 Points

Looks really close! There are a couple of things that need to be adjusted. To get a better idea of the issues, you can click on the "Preview" button in the challenge and you'll see a few syntax errors.

  • You'll want to wrap your if statement in parentheses like this:
if (word.startsWith("http"))
  • You'll need to add a semicolon to the end of your results.add(word) call:
results.add(word);
  • Make sure to return results at the end of the getExternalLinks method:
return results;
  • It looks like there's an extra getExternalLinks method at the end of the file that needs to be removed:
  public getExternalLinks(){

  }
Sean M
Sean M
7,344 Points
Sean M
Sean M
7,344 Points

This answer is for future reference to students. It definitely took me some time to fully grasp this one.

  1. Creating a public class that is a list of strings. This class is named getExternalLinks

    public List<String> getExternalLinks() {

  2. Introducing the list that will contain strings. We will name the lists "results". This information is a new Array List that will contain Strings.

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

  3. for each word, which is a string, we want to get every word (to check if it has htttp which is the next step)

    for (String word: getWords()) {

  4. If the word starts with "http", add the word. 

      if (word.startsWith("http")) {
    results.add(word);
  }
}
return results;
}
}