Learning Java Program

import java.util.Scanner;
class diamondShape
{
      public static void main(String[] args)
    {
        System.out.print("Enter number of rows: ");
        Scanner in = new Scanner(System.in);
        int num=in.nextInt();
        for(int i=1;i<=num;i++)
        {
           for(int j=num;j>=i;j--)
           {
            System.out.print(" ");
           }
           for(int m=1;m<=i;m++)
           {
           System.out.print(" *");
           }
       System.out.print("\n");
       }    
       for(int i=1;i<=num;i++)
       {
           for(int j=1;j<=i;j++)
           {
           System.out.print(" ");
           }
           for(int m=num;m>=i;m--)
           {
           System.out.print(" *");
           }
        System.out.print("\n");
        }   
    }
   
}