How to sort Arraylist by many catogories

Question

Here I' comparing but only the title of the book. But after that I want to compare it with the author and the book no. As I know there must be only one override method. So please help me on this.

@Override

public int compareTo(Book bk) {

return this.bookTitle.compareTo(bk.bookTitle);
}

Siva · Accepted Answer · 2014-03-28T09:31:27.083

You have to implement different comparators for different sorting types and pass them for Collections.Sort method. See Comparator

Class AuthorSort implements Comparator<Book>
{

   public int compare(Book b1, Book b2){
       // do comparision on Author
    }

}

Implements Book Number Sorting

Class BookNoSort implements Comparator<Book>
{

   public int compare(Book b1, Book b2){
       // do comparision on Book Number
    }

}

Call Sort method on Collections class and provide different implentation

Collections.sort(list, new BookNumberSort());
Collections.sort(list, new AuthorSort());

score 0 · Answer 2 · answered Mar 22 '14 at 05:46

0

Google Comparator

class BookAuthorComparator implements Comparator<Book>{
    public int compare(Book b1, Book b2){
        return b1.getAuthor().compareTo(b2.getAuthor());
    }
}

Collections.sort(bookList, new BookAuthorCompartor());

answered Mar 22 '14 at 05:46

sidgate

14,650
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How can I get 2 return types for title and author seperatly – user9480 Mar 22 '14 at 05:51
what do you mean by 2 return types? what is your use case? – sidgate Mar 22 '14 at 05:52

score 0 · Answer 3 · edited May 23 '17 at 12:11

0

Write your own Comparator by implementing Compareable

Refer this How to compare objects by multiple fields

edited May 23 '17 at 12:11

Community

1
1

answered Mar 22 '14 at 05:49

Dipika

584
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12

score 0 · Answer 4 · answered Mar 22 '14 at 05:57

you could use anonymous inner class as:

Collections.sort(bookList, new Comparator<Book>() {
        @Override
        public int compare(Book b1, Book b2) {
            return b1.property.compare(b2.property);
        }
    });

if you want sorting to be performed on title or author just change

return b1.getTitle().compare(b2.getTitle());

or

return b1.getAuthor().compare(b2.getAuthor());

How to sort Arraylist by many catogories

4 Answers4