java checking the amount of duplicates in array

/**
 * @author lautturi.com
 * Java example: java count duplicates in int array
 */
import java.util.*;

public class Lautturi {

	public static void main(String[] args) {
		int[] numbers = { 11,4,12,7,55,8,12,8,13,55,12,7 };
		Arrays.sort(numbers);
        int previous = numbers[0] - 1;
        
        int dupCount = 0;

        for (int i = 0; i < numbers.length; ++i) {
            if (numbers[i] == previous) {
                ++dupCount;
            } else {
                previous = numbers[i];
            }
        }
        System.out.println("There were " + dupCount + " duplicates in the array.");
		
	}
}

output:

There were 5 duplicates in the array.