Thread: Nested Loops & Processing Strings

I am reading a file from the user and now I have to count the number of characters, blank spaces, digits, "other characters", words, and lines in a text file using a loop.

I am having trouble considering what methods of class Character to use and how to increment a counter for each type of character inside a loop.

Here is what I have thus far: *I only have the basic beginning*

import java.util.*;
import java.io.*;
 
 
public class Reader
{
  public static void main (String args[]) throws IOException {
 
  Scanner console = new Scanner(System.in);
 
 
  String filename;
  String last;
 
 
//Declared FileReader and Scanner for the user
 
 
  System.out.println("Please enter the name of the file to be read. ");
  filename = console.nextLine();
 
  FileReader  inputFile = new FileReader(filename);
  Scanner input = new Scanner(inputFile);
 
 
// Loops to count number of characters, etc.
 
 
    while (input.hasNextLine()) {
 
last = input.nextLine();
         System.out.println(last);
  }
 }
}

I have created another program before hand to decide the characters, but I don't know if I could increment this into my main.

 if (asciiValue >= 49 && asciiValue <= 57)
    System.out.println("Input is a number");
      else if (asciiValue >= 65 && asciiValue <= 90)
    System.out.println("Input is an uppercase letter");
      else if (asciiValue >= 97 && asciiValue <= 122)
    System.out.println("Input is a lowercase letter");
     else if (asciiValue == 32)
    System.out.println("Input is a space");
     else
    System.out.println("Input is an other character");

You need to store some variables for each of the digits

long numChars = 0, numDigits = 0, numSpaces = 0;

Then you need to declare a BufferedReader, because they are just so much easier. (Or Scanner, whatever you prefer)

/*
 * Precondition: fr is a FileReader
 */
BufferedReader br = new BufferedReader(fr);

then you need to either use a for loop or a while loop to cycle through your code. (A while loop seems more natural here)

String currentLine = br.readLine();
while(currentLine != null)
{
 
}

Then, inside of your while loop, you need to figure out if each character is a digit, space, or something else (character)
Luckily, Character does have some methods to help you out, conveniently explained here
But wait! We can't use the Character class on Strings, so we need some way to convert. Searching through String's API, we find charAt(int index) and toCharArray(). Deciding to use toCharArray for easier use, we use that method to convert, and use a for loop to cycle through the array.

char[] charArray = currentLine.toCharArray();
Character currentChar;
for(int i = 0; i < charArray.length; i++)
{
  currentChar = charArray[i];
}

But now we need to decide what the char is, and respectively increment the correct long.
Going back to Characters API, we find the isDigit() and the isWhitespace() methods, and if not either of those, it is some kind of character. Using those, we get

  if(Character.isDigit(currentChar))
    numDigits++;
  else if(Character.isWhitespace(currentChar))
    numSpaces++;
  else
    numChars++;

Then you need to update our line with (outside our for loop)

currentLine = br.nextLine();

And that is all you need to get those, but you still ahve an open reader, so we end this part of the program (Unless you need the reader elsewhere) with

br.close();

(Note that is outside the while loop)

That error message is self explanatory, you did not give your variable an initial value.

String s;
if(5 == 19) {
    s = "hello";
}
System.out.println(s);

In the above code what do you expect to be displayed?

char currentChar = ...;

No need to use objects when it isn't necessary.

I can't do what?

Oops! Misread your post.

char one = '1';
char two = 't';
System.out.println(Character.isDigit(one));
System.out.println(Character.isDigit(two));

Produces the exact output I expect: true false.

Declaring a variable and initialising it are two different things.

Declare
String s;

Initialise
s = "hello";

Declare and initialise
String s = "hello";