javasortingcollectionscomparable

How do I make 2 comparable methods in only one class?


I've got one class, that I sort it already by one attribute. Now I need to make another thing, that I need to create another way to sort my data. How can I make it, so I can choose between the two methods. The only command I know is Collections.sort that will pick up the method compareTo from the class I want to compare its data.

Is it even possible?


Solution

  • What you need to do is implement a custom Comparator. And then use:

    Collections.sort(yourList, new CustomComparator<YourClass>());
    

    Specifically, you could write: (This will create an Anonymous class that implements Comparator.)

    Collections.sort(yourList, new Comparator<YourClass>(){
        public int compare(YourClass one, YourClass two) {
            // compare using whichever properties of ListType you need
        }
    });
    

    You could build these into your class if you like:

    class YourClass {
    
        static Comparator<YourClass> getAttribute1Comparator() {
            return new Comparator<YourClass>() {
                // compare using attribute 1
            };
        }
    
        static Comparator<YourClass> getAttribute2Comparator() {
            return new Comparator<YourClass>() {
                // compare using attribute 2
            };
        }
    }
    

    It could be used like so:

    Collections.sort(yourList, YourClass.getAttribute2Comparator());