Answered: m should count and display the number…

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Question

Chapter 4. PC #6. File Letter Counter (page 264)

Write a program that asks the user to enter the name of a file, and then asks the user to enter a character. The program should count and display the number of times that the specified character appears in the file.

Class name: FileLetterCounter

Hints:

Hint 1. To read a single character from the keyboard, you need to read a full line and then take the first character in position 0.

Hint 2. To count the occurrences of a given characters in a file you need to read the file line-by-line using a while loop, then for each line check all characters in all positions and increment the character counter for each occurrence. This will require to have a for-loop nested inside the while-loop.

Here is a working code. Modify this code so it will pass the test cases.

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class FileRead {
public static void main(String[] args) throws FileNotFoundException {
Scanner keyboard = new Scanner(System.in);
System.out.println("Please enter the file name or type QUIT to exit:");
String filename = keyboard.nextLine();
if (filename.equalsIgnoreCase("Quit"))
return;

File myFile = new File(filename);
while (!myFile.exists()) {
System.out.println("File: " + filename + " does not exist.");
System.out.println("Please enter the file name again or type QUIT to exit:");
filename = keyboard.nextLine();
if (filename.equalsIgnoreCase("Quit")) {
return;
}
myFile = new File(filename);
}

Scanner inputFile = new Scanner(myFile);
int lines = 0;
while (inputFile.hasNext()) {
String str = inputFile.nextLine();
lines++;
System.out.println(lines + ": " + str);
}
inputFile.close();
}
}

Test Case 1

Please enter the file name or type QUIT to exit:\n
QUITENTER

Test Case 2

Please enter the file name or type QUIT to exit:\n
badfilename.txtENTER
File: badfilename.txt does not exist.\n
Please enter the file name again or type QUIT to exit:\n
quitENTER

Test Case 3

Please enter the file name or type QUIT to exit:\n
input.txtENTER
Please enter a character: \n
oENTER
Letter 'o' occurs 4 times in the file 'input.txt'.\n

Test Case 4

Please enter the file name or type QUIT to exit:\n
letters.txtENTER
Please enter a character: \n
aENTER
Letter 'a' occurs 82 times in the file 'letters.txt'.\n

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