RECURSION - Introduction to Java Programming: Comprehensive Version - page 730

For example, reverseDisplay("abcd") displays dcba . Write a test program
that prompts the user to enter a string and displays its reversal.
*18.10 ( Occurrences of a specified character in a string ) Write a recursive method that
finds the number of occurrences of a specified letter in a string using the follow-
ing method header:

public static int count(String str, char a)

For example, count("Welcome", 'e') returns 2 . Write a test program that
prompts the user to enter a string and a character, and displays the number of
occurrences for the character in the string.
*18.11 ( Sum the digits in an integer using recursion ) Write a recursive method that
computes the sum of the digits in an integer. Use the following method header:

public static int sumDigits( long n)

+ + =

For example, sumDigits(234) returns 2 9. Write a test program

that prompts the user to enter an integer and displays its sum.

3 4

Section 18.5
**18.12

( Print the characters in a string reversely ) Rewrite Programming Exercise 18.9
using a helper method to pass the substring high index to the method. The
helper method header is:

public static void reverseDisplay(String value, int high)

*18.13

( Find the largest number in an array ) Write a recursive method that returns the
largest integer in an array. Write a test program that prompts the user to enter a
list of eight integers and displays the largest element.

*18.14

( Find the number of uppercase letters in a string ) Write a recursive method
to return the number of uppercase letters in a string. Write a test program that
prompts the user to enter a string and displays the number of uppercase letters in
the string.

*18.15

( Occurrences of a specified character in a string ) Rewrite Programming Exer-
cise 18.10 using a helper method to pass the substring high index to the method.
The helper method header is:

public static int count(String str, char a, int high)

*18.16

( Find the number of uppercase letters in an array ) Write a recursive method
to return the number of uppercase letters in an array of characters. You need to
define the following two methods. The second one is a recursive helper method.

public static int count( char [] chars)
public static int count( char [] chars, int high)

Write a test program that prompts the user to enter a list of characters in one line
and displays the number of uppercase letters in the list.

*18.17

( Occurrences of a specified character in an array ) Write a recursive method that
finds the number of occurrences of a specified character in an array. You need to
define the following two methods. The second one is a recursive helper method.

public static int count( char [] chars, char ch)
public static int count( char [] chars, char ch, int high)