Java Reference
In-Depth Information
*20.7
(
Fibonacci series
) Modify Listing 20.2, ComputeFibonacci.java, so that the
program finds the number of times the
fib
method is called. (
Hint
: Use a static
variable and increment it every time the method is called.)
Section 20.4
*20.8
(
Print the digits in an integer reversely
) Write a recursive method that displays
an
int
value reversely on the console using the following header:
public static void
reverseDisplay(
int
value)
For example,
reverseDisplay(12345)
displays
54321
. Write a test pro-
gram that prompts the user to enter an integer and displays its reversal.
*20.9
(
Print the characters in a string reversely
) Write a recursive method that dis-
plays a string reversely on the console using the following header:
public static void
reverseDisplay(String value)
For example,
reverseDisplay("abcd")
displays
dcba
. Write a test pro-
gram that prompts the user to enter a string and displays its reversal.
*20.10
(
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 fol-
lowing 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.
*20.11
(
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 Write a test program
that prompts the user to enter an integer and displays its sum.
2
+
3
+
4
=
9.
Section 20.5
**20.12
(
Print the characters in a string reversely
) Rewrite Exercise 20.9 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)
*20.13
(
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.
*20.14
(
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.
*20.15
(
Occurrences of a specified character in a string
) Rewrite Exercise 20.10
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)
