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Java Java Data Structures - Retired Organizing Data Comparable

Posted by ashmagupta
ashmagupta
6,595 Points

Pls help me. I am stuck here like forever.

This is the error showing on preview . ./com/example/BlogPost.java:31: error: cannot find symbol return mCreationdate.compareTo(blogpost.mCreationdate); ^ symbol: variable mCreationdate location: variable blogpost of type BlogPost ./com/example/BlogPost.java:31: error: cannot find symbol return mCreationdate.compareTo(blogpost.mCreationdate); ^ symbol: variable mCreationdate location: class BlogPost 2 errors

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

import java.util.Date;
// Assuming public class implements comparable//
public class BlogPost implements Comparable{
  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;
  }
// producing compareTo method//

  public int compareTo(Object obj){
  BlogPost blogpost = (BlogPost) obj;
  if (equals(obj)){
  return 0; }else 
  { return 1;}

   //cast the object to file//
  //Chronologically order creationdate//
  int dateCmp = mCreationDate.compareTo(blogpost.mCreationDate);
    if (dateCmp == 0) {
    return mCreationdate.compareTo(blogpost.mCreationdate);
    }
    return dateCmp;
  }


  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;
  }
}

2 Answers

andren
andren
28,558 Points
andren
andren
28,558 Points

There are a couple of issues:

The first is in your first if statement:

if (equals(obj)) {
  return 0; }
else { 
  return 1;
}

You tell Java to either return 0 or 1 based on the comparison, that means that the method will always return a value at this point, when a method returns a value it stops running. Which means that all of the code below this if statement will never be run in any situation.

This can be fixed by simply removing the else statement.

The second issue is that the mCreationDate field is private, that means that you can't directly access it from the cast BlogPost object. You have to use the getCreationDate getter that has been setup to retrieve that field.

The third issue is that you misspell mCreationDate in this line:

return mCreationdate.compareTo(blogpost.mCreationdate);

You forgot to capitalize the D in the first mCreationDate.

If you fix all of those issues like this:

package com.example;

import java.util.Date;
// Assuming public class implements comparable//
public class BlogPost implements Comparable{
  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;
  }
// producing compareTo method//

  public int compareTo(Object obj){
  BlogPost blogpost = (BlogPost) obj;
  // Remove else statement
  if (equals(obj)){
    return 0; 
  }

   //cast the object to file//
  //Chronologically order creationdate//
  // Change mCreationDate to getCreationDate()
  int dateCmp = mCreationDate.compareTo(blogpost.getCreationDate());
    if (dateCmp == 0) {
    // Change mCreationDate to getCreationDate() and fix typo
    return mCreationDate.compareTo(blogpost.getCreationDate());
    }
    return dateCmp;
  }


  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;
  }
}

Then your code will work

ashmagupta
ashmagupta
6,595 Points

Hi Andren, Thanks for replying. When i remove else from the if statement, the code didn't pass and it showed more error.

andren
andren
28,558 Points
andren
andren
28,558 Points

That's odd, I tested the code that I posted above before submitting the answer so it should work. The challenges can sometimes be a bit buggy, so maybe try to restart the challenge and then copy and paste in the code from my answer. That should work correctly.

ashmagupta
ashmagupta
6,595 Points
ashmagupta
ashmagupta
6,595 Points

Thanks, Yep, its passed.