How to count uppercase and lowercase letters in a string?

Question

yo, so im trying to make a program that can take string input from the user for instance: "ONCE UPON a time" and then report back how many upper and lowercase letters the string contains:

output example: the string has 8 uppercase letters the string has 5 lowercase letters, and im supposed to use string class not arrays, any tips on how to get started on this one? thanks in advance, here is what I have done so far :D!

import java.util.Scanner;
public class q36{
    public static void main(String args[]){

        Scanner keyboard = new Scanner(System.in);
        System.out.println("Give a string ");
        String input=keyboard.nextLine();

        int lengde = input.length();
        System.out.println("String: " + input + "\t " + "lengde:"+ lengde);

        for(int i=0; i<lengde;i++) {
            if(Character.isUpperCase(CharAt(i))){

            }
        }
    }
}

Answer 1

Simply create counters that increment when a lowercase or uppercase letter is found, like so:

for (int k = 0; k < input.length(); k++) {
    /**
     * The methods isUpperCase(char ch) and isLowerCase(char ch) of the Character
     * class are static so we use the Class.method() format; the charAt(int index)
     * method of the String class is an instance method, so the instance, which,
     * in this case, is the variable `input`, needs to be used to call the method.
     **/
    // Check for uppercase letters.
    if (Character.isUpperCase(input.charAt(k))) upperCase++;

    // Check for lowercase letters.
    if (Character.isLowerCase(input.charAt(k))) lowerCase++;
}

System.out.printf("There are %d uppercase letters and %d lowercase letters.",upperCase,lowerCase);

Answer 2

java 8

private static long countUpperCase(String inputString) {
        return inputString.chars().filter((s)->Character.isUpperCase(s)).count();
    }

    private static long countLowerCase(String inputString) {
        return inputString.chars().filter((s)->Character.isLowerCase(s)).count();
    }

Answer 3

The solution in Java8:

private static long countUpperCase(String s) {
    return s.codePoints().filter(c-> c>='A' && c<='Z').count();
}

private static long countLowerCase(String s) {
    return s.codePoints().filter(c-> c>='a' && c<='z').count();
}

Answer 4

You can try the following code :

public class ASCII_Demo
{
    public static void main(String[] args)
    {
        String str = "ONCE UPON a time";
        char ch;
        int uppercase=0,lowercase=0;
        for(int i=0;i<str.length();i++)
        {
            ch = str.charAt(i);
            int asciivalue = (int)ch;
            if(asciivalue >=65 && asciivalue <=90){
                uppercase++;
            }
            else if(asciivalue >=97 && asciivalue <=122){
                lowercase++;
            }
        }
        System.out.println("No of lowercase letter : " + lowercase);
        System.out.println("No of uppercase letter : " + uppercase);
    }
}

Answer 5

Use regular expressions:

public Counts count(String str) {
    Counts counts = new Counts();
    counts.setUpperCases(str.split("(?=[A-Z])").length - 1));
    counts.setLowerCases(str.split("(?=[a-z])").length - 1));
    return counts;
}

Answer 6

import java.io.*;
import java.util.*;
public class CandidateCode {
    public static void main(String args[] ) throws Exception {
         int count=0,count2=0,i;
        Scanner sc = new Scanner(System.in);
         String s = sc.nextLine();
         int n = s.length();
         for( i=0; i<n;i++){
             if(Character.isUpperCase(s.charAt(i)))
                 count++;
             if(Character.isLowerCase(s.charAt(i))) 
             count2++;
         }
             System.out.println(count);
             System.out.println(count2);
         }



}

Answer 7

You can increase the readability of your code and benefit from some other features of modern Java here. Please use the Stream approach for solving this problem. Also, please try to import the least number of libraries. So, avoid using .* as much as you can.

import java.util.Scanner;

public class q36 {
    public static void main(String[] args) {
        Scanner keyboard = new Scanner(System.in);
        System.out.println("Give a string ");
        String input = keyboard.nextLine();
        int numberOfUppercaseLetters =
                Long.valueOf(input.chars().filter(c -> Character.isUpperCase(c)).count())
                        .intValue();
        int numberOfLowercaseLetters =
                Long.valueOf(input.chars().filter(c -> Character.isLowerCase(c)).count())
                        .intValue();
        System.out.println("The lenght of the String is " + input.length()
                + " number of uppercase letters " + numberOfUppercaseLetters
                + " number of lowercase letters " + numberOfLowercaseLetters);
    }
}

Sample input:

saveChangesInTheEditor

Sample output:

The lenght of the String is 22 number of uppercase letters 4 number of lowercase letters 18

Answer 8

You simply loop over the content and use the Character features to test it. I use real codepoints, so it supports supplementary characters of Unicode.

When dealing with code points, the index cannot simply be incremented by one, since some code points actually read two characters (aka code units). This is why I use the while and Character.charCount(int cp).

/** Method counts and prints number of lower/uppercase codepoints. */
static void countCharacterClasses(String input) {
    int upper = 0;
    int lower = 0;
    int other = 0;

    // index counts from 0 till end of string length
    int index = 0;
    while(index < input.length()) {
        // we get the unicode code point at index
        // this is the character at index-th position (but fits only in an int)
        int cp = input.codePointAt(index);
        // we increment index by 1 or 2, depending if cp fits in single char
        index += Character.charCount(cp);

        // the type of the codepoint is the character class
        int type = Character.getType(cp);
        // we care only about the character class for lower & uppercase letters
        switch(type) {
            case Character.UPPERCASE_LETTER:
                upper++;
                break;
            case Character.LOWERCASE_LETTER:
                lower++;
                break;
            default:
                other++;
        }
    }

    System.out.printf("Input has %d upper, %d lower and %d other codepoints%n",
                      upper, lower, other);
}

For this sample the result will be:

// test with plain letters, numbers and international chars:
countCharacterClasses("AABBÄäoßabc0\uD801\uDC00");
      // U+10400 "DESERET CAPITAL LETTER LONG I" is 2 char UTF16: D801 DC00

Input has 6 upper, 6 lower and 1 other codepoints

It count the german sharp-s as lowercase (there is no uppercase variant) and the special supplement codepoint (which is two codeunits/char long) as uppercase. The number will be counted as "other".

Using Character.getType(int cp) instead of Character.isUpperCase() has the advantage that it only needs to look at the code point once for multiple (all) character classes. This can also be used to count all different classes (letters, whitespace, control and all the fancy other unicode classes (TITLECASE_LETTER etc).

For a good background read on why you need to care about codepoints und units, check out: http://www.joelonsoftware.com/articles/Unicode.html