LeetCode

Lambda Expression

Sort function, Compare function

Posted by Clover on February 2, 2021

Collections sort

compare must return int when override For example, we define a new class Book

Use lambda expression

Collections.sort(listBooks, (b1, b2) -> (int) (b1.getPrice() - b2.getPrice()));

Create new comparator for Book class

class SortbyPrice implements Comparator<Book>
{
  public int compare(Book b1, Book b2) {
    return (int)(b1.getPrice() - b2.getPrice());
  }
}

Collections.sort(listBooks, new SortbyPrice());

Use inner class of Comparator

Collections.sort(listBooks, new Comparactor<>(){
  @Override
  public int compare(Book b1, Book b2) {
    return (int)(b1.getPrice() - b2.getPrice());
  }
});