Exceptions Aren\'t Always Errors File CountLetters.java contains a program that
ID: 3767170 • Letter: E
Question
Exceptions Aren't Always Errors
File CountLetters.java contains a program that reads a word from the user and prints the number of occurrences of each letter in the word. In reviewing the code, note that the word is converted to all upper case first, then each letter is translated to a number in the range 0..25 (by subtracting 'A' or decimal 65) for use as an index. No test is done to ensure that the characters are in fact letters.
Add the proper comment section, run CountLetters and enter a phrase, that is, more than one word with spaces or other punctuation in between. It should throw an ArrayIndexOutOfBoundsException, because
non-letter will generate an index that is not between 0 and 25. It might be desirable to allow non-letter characters, but not count them. Of course, you could explicitly test the value of the character to see if it is between 'A' and 'Z'. However, an alternative is to go ahead and use the translated character as an index, and catch an ArrayIndexOutOfBoundsException if it occurs. Since you want don't want to do anything when a non-letter occurs, the handler will be empty. Modify this method to do this as follows:
Put the body of the first for loop in a try. (5 points)
Add a catch that catches the exception, but don't do anything with it. (5 points)
Now modify the body of the catch so that it prints a useful message (e.g., "Not a letter") followed by the exception. (5 points)
****************************************************************************
CountLetters.java
****************************************************************************
import java.util.Scanner;
public class CountLetters
{
public static void main(String[] args)
{
int[]
counts
=
new
int[26];
Scanner scan
=
new
Scanner(System.in);
//get
word from user
System.out.print("
Enter a single word (letters only): ");
String word = scan.nextLine();
//convert to all upper case word = word.toUpperCase();
//count frequency of each letter in string for (int i=0; i < word.length(); i++)
counts[word.charAt(i)-'A']++;
//print frequencies System.out.println();
for (int i=0; i < counts.length; i++) if (counts [i] != 0)
System.out.println((char)(i +'A') + ": " + counts[i]);
}
}
int[]
counts
=
new
int[26];
Scanner scan
=
new
Scanner(System.in);
//get
word from user
System.out.print("
Enter a single word (letters only): ");
Explanation / Answer
import java.util.Scanner;
public class LetterCount
{
public static void main(String[] args) {
Scanner inp= new Scanner(System.in);
String str;
char ch;
int count=0;
System.out.println("Enter the string:");
str=inp.nextLine();
while(str.length()>0)
{
ch=str.charAt(0);
int i=0;
while(str.charAt(i)==ch)
{
count =count+i;
i++;
}
str.substring(count);
System.out.println(ch);
System.out.println(count);
}
}
}
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