Java: Count the letters, spaces, numbers and other characters of an input string

Last update on May 12 2025 13:17:45 (UTC/GMT +8 hours)

Count Characters in String

Write a Java program to count letters, spaces, numbers and other characters in an input string.

Test Data:
The string is : Aa kiu, I swd skieo 236587. GH kiu: sieo?? 25.33

Pictorial Presentation:

Sample Solution:

Java Code:

import java.util.Scanner;

public class Exercise38 {
    public static void main(String[] args) {
        // Define a test string containing letters, numbers, spaces, and other characters
        String test = "Aa kiu, I swd skieo 236587. GH kiu: sieo?? 25.33";
        
        // Call the count method to analyze the characters in the test string
        count(test);
    }

    public static void count(String x) {
        // Convert the input string to a character array
        char[] ch = x.toCharArray();
        
        // Initialize counters for letters, spaces, numbers, and other characters
        int letter = 0;
        int space = 0;
        int num = 0;
        int other = 0;
        
        // Iterate through the character array to categorize characters
        for (int i = 0; i < x.length(); i++) {
            // Check if the character is a letter
            if (Character.isLetter(ch[i])) {
                letter++;
            }
            // Check if the character is a digit (number)
            else if (Character.isDigit(ch[i])) {
                num++;
            }
            // Check if the character is a space
            else if (Character.isSpaceChar(ch[i])) {
                space++;
            }
            // Character falls into the "other" category if none of the above conditions are met
            else {
                other++;
            }
        }
        
        // Display the original string
        System.out.println("The string is : Aa kiu, I swd skieo 236587. GH kiu: sieo?? 25.33");
        
        // Display the counts of letters, spaces, numbers, and other characters
        System.out.println("letter: " + letter);
        System.out.println("space: " + space);
        System.out.println("number: " + num);
        System.out.println("other: " + other);
    }
} 

Explanation:

In the exercise above -

• The string to be analyzed is stored in the 'test' variable.
• The "count()" method takes a string 'x' as its parameter.
• Inside the "count()" method, the "toCharArray()" method is used to convert the input string x into an array of characters 'ch'.
• Four variables (letter, space, num, and other) are initialized to zero. These variables will be used to count the respective types of characters in the string.
• A for loop iterates through each character in the 'ch' array.
• Inside the loop, it checks the type of each character using various "Character" class methods like isLetter(), isDigit(), and isSpaceChar(). Depending on the type, it increments the corresponding counter variable (letter, num, space, or other).
• Finally, it prints the original string and the counts of each character type.

Sample Output:

The string is :  Aa kiu, I swd skieo 236587. GH kiu: sieo?? 25.33
letter: 23                                                                                                    
space: 9                                                                                                      
number: 10                                                                                                    
other: 6

Flowchart:

For more Practice: Solve these Related Problems:

• Modify the program to count uppercase and lowercase letters separately.
• Write a program to find the most frequent character in a string.
• Ignore punctuation while counting letters.
• Implement character counting using a hash map.

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