Question

Possible Duplicate:
Sort arrays of primitive types in descending order
Java : How to sort an array of floats in reverse order?
How do I reverse an int array in Java?

The following code will sort the array in ascending order :

int a[] = {30,7,9,20};
Arrays.sort(a);
System.out.println(Arrays.toString(a));

I need to sort it in descending order. How do I use Comparator to do this?

Please help.

Answer 1

For primitive array types, you would have to write a reverse sort algorithm:

Alternatively, you can convert your int[] to Integer[] and write a comparator:

public class IntegerComparator implements Comparator<Integer> {

    @Override
    public int compare(Integer o1, Integer o2) {
        return o2.compareTo(o1);
    }
}

or use Collections.reverseOrder() since it only works on non-primitive array types.

and finally,

Integer[] a2 = convertPrimitiveArrayToBoxableTypeArray(a1);
Arrays.sort(a2, new IntegerComparator()); // OR
// Arrays.sort(a2, Collections.reverseOrder());

//Unbox the array to primitive type
a1 = convertBoxableTypeArrayToPrimitiveTypeArray(a2);