Thread: Help with sorting Employee class

Originally Posted by sunilshiwankar

A Employee Class with fields of name , age , address, salary and want to sort the objects lists by there salary and also by there name (Two way sorting on a same custom class) using comparator or comparable? How we do it?

Comparable must be implemented into the class of the objects to sort, so you can have only 1 ordering with Comparable for a given type, that should be the "natural" ordering of the objects (the order on name of Employee can be seen as the "natural" order).
Comparator must be implemented in other, distinct, classes, so you can have N orderings with Comparator for a given type.

Please, see, documentation of Comparable/Comparator, implement these interfaces and for any precise doubts, ask.

Originally Posted by sunilshiwankar

can u give me the example of implementing comparator with two ordering ?

In a very sketchy way:

public class Book implements Comparable<Book> {
    private String title;
    private String publisher;
 
    // ... constructor(s), getter/setter methods, toString(), etc. ...
 
    public int compareTo(Book other) {
        return getTitle().compareTo(other.getTitle());
    }
}
 
 
public class BookPublisherComparator implements Comparator<Book> {
    public int compare(Book book1, Book book2) {
        return book1.getPublisher().compareTo(book2.getPublisher());
    }
}

If you a have a primitive field, obviously, you can't use compareTo (title/publisher are String, that is Comparable and has compareTo). For primitives, just use < , > , etc... (or wrap into Integer, etc... or use e.g. compare(int x, int y) of Integer available since Java 7).