Comparable : Java Glossary

To implement Comparable you must write only one method: compareTo. It is typically added to an existing class to describe the natural order of that class. compareTo compares this object with another.

public int compareTo( Object o );

Beware of using subtraction in writing Comparabless rather than < > if there is any possibility you will be using numbers large enough to overflow and give the wrong sign comparing them with subtraction.

Comparable Using Generics

Comparable Gotcha

// base class
class SalesTaxItem implements Comparable<SalesTaxItem>
{
...
}

The best way I know of to bypass the problem is to write both classes without the implements Comparable. Then write two Comparators instead.

Descending/Inverse/Reverse Order with reverseOrder

If you have a Comparator or Comparable of some kind, you can convert it into one that sorts into the reverse of the usual order. E.g. if the original sorts alphabetically, the new one will sort in reverse alphabetical order. Here is how you use it:

If you don't have a suitable base Comparator, just write an ordinary Comparator from scratch and reverse the operands to each compare inside it, or return - result instead of result.

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