Java Program on Bubble Sort

Write a program to input twenty names in an array. Arrange these names in  descending order of alphabets  using the bubble sort technique.  

import java.util.Scanner;
public class ArrangeNames
{
    public static void main(String []args)
    {
        String a [] =new  String [20];
        Scanner scan=new Scanner(System.in);
        System.out.println("Please enter the twenty names");
        for (int i = 0; i <= 19; i++)
        {
            a [i]= scan.next();
        }
        String t;
        for (int i=0; i<19; i++ )
        {
            for (int j = 0; j < 20 -i-1; j++)
            {
                if  (a[j].compareTo (a[j+ 1]) >0)
                {
                    t = a[j] ;
                    a[j] =a[j+1];
                    a[j+1]= t;
                }       
            }
        }
        System.out.println("Sorted element are:");
        for (int k=19; k> 0; k--) 
        {
            System.out.println(a[k]);
        }
    }
}