Chapter 12, Problem 1E

Explanation of Solution

Program code:

// class definition

class Main

{

  //main method

  public static void main(String[] args)

  {

    //loop that iterates for the values

    for(int i=0;i<=4;i++)

    //display the starstring

    System.out.println(starString(i));

  }

  //method definition

  public static String starString(int n)

  {

    //condition to validate the value passed

    if (n < 0)

    {

        //throw illegal argument exception

        throw new IllegalArgumentException();

    }

    //else part for value 0 

    else if (n == 0)

    {

        //return *

        return "*";

    }

    //else part

    else

    {

        //return the string

        return starString(n - 1) + starString(n - 1);

    }

}

}

Explanation:

• The method “starString” is used to print the star to the console and it made by validating the value of n using “if” condition.
• If the value of n is less than 0 then illegal argument exception is passed.
• If the value of n is equal to 0 then the “*” is returned.
• If the value is greater than 0 then recursively the function “starString” is executed to print the string.

Sample Output

Output

*

**

****

********

****************