Sorting int array in descending order [duplicate]

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);