如何将此FOR循环转换为WHILE循环，以便它也计入辅音？ （JAVA）

Question

How do I convert this FOR loop into a WHILE loop so that it also counts for Consonants? I know how to do a basic counter using While loop so far...

import java.util.Scanner;

public class VowelsCount {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.print("Input a string: ");
        String str = in.nextLine();

        System.out.print("Number of Vowels in the string: " + vowCount(str) + "\n");
    }

    public static int vowCount(String str) {
        int count = 0;
        for (int index = 0; index < str.length(); index++) {
            if (str.charAt(index) == 'a' || str.charAt(index) == 'e' ||
                str.charAt(index) == 'i' || str.charAt(index) == 'o' ||
                str.charAt(index) == 'u') {
                count++;
            }
        }
        return count;
    }
}

Answer 1

A while() loop has at its argument a termination statement , that means instead of initialising, and incrementing your index you have to set your termination as while parameter. EDIT the index variable has to be initialised before your loop.

In your case:

while(index != str.length()){
     //rest of the statement, those from your for loop
     index++;
}

Answer 2

This is ready LetterCount class, that could incapsulate all glogic for letter count:

public final class LetterCount {

    private final String str;
    private final int vowel;
    private final int consonant;

    public static LetterCount create(String str) {
        int[] count = count(str);
        return new LetterCount(str, count[0], count[1]);
    }

    private static int[] count(String str) {
        int i = str.length();
        int[] count = new int[2];

        while (--i >= 0) {
            char ch = Character.toLowerCase(str.charAt(i));

            if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u')
                count[0]++;
            else if (ch >= 'a' && ch <= 'z')
                count[1]++;
        }

        return count;
    }

    private LetterCount(String str, int vowel, int consonant) {
        this.str = str;
        this.vowel = vowel;
        this.consonant = consonant;
    }

    public String getStr() {
        return str;
    }

    public int getVowel() {
        return vowel;
    }

    public int getConsonant() {
        return consonant;
    }

}

Answer 3

You can count consonants by initializing another variable, add it by 1 in else condition when your if criteria is not met. for while loop you can do something like this.

int countVow = 0;
int index = 0;
while(index != str.length())
{
    if(vowel)
    {
        countVow++;
    }

    index++
}
int countCon = index = countVow;

Answer 4

Here is a function count that counts both consonants and vowels, using a while loop (although the kind of loop doesn't matter really):

import java.util.Scanner;

public class VowelsCount {
    public static void main(String[] args) {
        @SuppressWarnings("resource")
        Scanner in = new Scanner(System.in);

        System.out.print("Input a string: ");
        String str = in.nextLine();

        Counts counts = count(str);

        System.out.println("Number of Vowels in the string: " + counts.getVowels());
        System.out.println("Number of Consonants in the string: " + counts.getConsonants());
    }

    public static Counts count(String str) {
        int vowCount = 0;
        int consCount = 0;

        str = str.toLowerCase();

        int i = str.length();
        while(i-- > 0) {
            char ch = str.charAt(i);
            if(ch >= 'a' && ch <= 'z') {
                switch(ch) {
                    case 'a':
                    case 'e':
                    case 'i':
                    case 'o':
                    case 'u':
                        vowCount++;
                        break;
                    default:
                        consCount++;
                        break;
                }
            }
        }

        return new Counts(vowCount, consCount);
    }

    public static final class Counts {
        private int vowels;
        private int consonants;

        public Counts(int vowels, int consonants) {
            this.vowels = vowels;
            this.consonants = consonants;
        }

        public int getVowels() {
            return vowels;
        }

        public int getConsonants() {
            return consonants;
        }
    }
}

Basically, how the function works is that it loops over all the characters in the string (in reverse), and then first checks if it is a letter (between a and z ), and if it is, then it must be either a vowel or a consonant. So we just need to check which one and increment the respective counter.

Answer 5

This is working fine:-

public static int vowCount(String str) {
            int count = 0;
            int index = 0;
            while (index < str.length()) {
                if (str.charAt(index) == 'a' || str.charAt(index) == 'e' || str.charAt(index) == 'i' || str.charAt(index) == 'o' || str.charAt(index) == 'u') {
                    count++;
                }
                index++;
            }
            return count;
        }

Answer 6

Replacing the for by a while is not required to also count the consonants.
Both can do that and a for that is better designed to iterate until a specific index seems better for your use case.

The idea would be to define a String of vowels and a String of consonants and for each encountered character you increment the counter according to the matching of these String s.

static final String vowels = "aei...";
static final String consonants = "bcdf...";

public static int[] vowCount(String str){
  int countV = 0;
  int countC = 0;
  for (int index = 0; index < str.length(); index++){
    String currentChar = str.substring(index, index+1);
    if (vowels.contains(currentChar)){
     countV++;
    }
    else if (consonants.contains(currentChar)){
     countC++;
    }
  }

  return new int[]{countV, countC};
}

I returned an array of int[] but you could also return an instance of a Count class you can define to hold the two data.