Import Java.util.*; Import Java.util.Scanner;

Short Answer

import java.util.*;
import java.util.Scanner;
public class AssertionExample
{
    public static void main( String args[] )
   {
       Scanner scanner = new Scanner( System.in );
       System.out.print( "Enter a number between 0 and 20: " );
       int value = scanner.nextInt();
       ---Code here---
       "Invalid number: " + value;
       System.out.printf( "You have entered %d\n", value );
   }
}
In the code above, when the user enters the number, the scanner.nextInt() method reads the number from the command line. In the blank line provided, create an assert statement that determines whether the entered  number is within the valid range (between 0 and 20). If the user entered a number that is out of range, then the "Invalid number" error should occur.