STRINGS - Introduction to Java Programming - page 363

9.4

( Occurrences of a specified character ) Write a method that finds the number of
occurrences of a specified character in a string using the following 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 followed by a character and displays the number
of occurrences of the character in the string.

**9.5

( Occurrences of each digit in a string ) Write a method that counts the occurrences
of each digit in a string using the following header:

public static int [] count(String s)

The method counts how many times a digit appears in the string. The return value
is an array of ten elements, each of which holds the count for a digit. For example,
after executing int[] counts = count("12203AB3") , counts[0] is 1 ,
counts[1] is 1 , counts[2] is 2 , and counts[3] is 2 .
Write a test program that prompts the user to enter a string and displays the num-
ber of occurrences of each digit in the string.

*9.6

( Count the letters in a string ) Write a method that counts the number of letters in a
string using the following header:

public static int countLetters(String s)

Write a test program that prompts the user to enter a string and displays the num-
ber of letters in the string.

*9.7

( Phone keypads ) The international standard letter/number mapping found on the
telephone is:

1 2 3

ABC DEF

4 5 6

GHI JKL MNO

7 8 9

PQRS TUV WXYZ

0

Write a method that returns a number, given an uppercase letter, as follows:

public static int getNumber( char uppercaseLetter)

Write a test program that prompts the user to enter a phone number as a string. The
input number may contain letters. The program translates a letter (upper- or lower-
case) to a digit and leaves all other characters intact. Here is a sample run of the
program:

Enter a string:
1-800-3569377

1-800-Flowers