CODEWITHSUNDEEP
javaindexingcharsubstringcounting
MasterWali
MasterWali

Reputation: 31

Counting a specific char in java

I want to count the number of times a certain character appears in a string, in this case it is the character 'a'. I know I can do this:

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

String testStr = "StackoverFlow Guess I'll Test The o's";
int counter = 0;
for (int i = 0; i<testStr.length(); i++ ){
    if(testStr.charAt(i) == ('o')){
        counter++;
    }
}
System.out.println("Number of o's:" + counter);
    }
}

But what am I doing wrong here:

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

    System.out.println("Enter String:");

    Scanner input = new Scanner(System.in);
    String inputStr = input.nextLine();
    int counterA = 0;

for(int i = 1; i<inputStr.length(); i++){
    if(inputStr.substring(i - 1, i).equals('a')){
    counterA++;
        }
    }
System.out.println("number of a's:" + counterA);

}
        }

Upvotes: 0

Views: 51

Answers (3)

maraca
maraca

Reputation: 8858

You have to be careful in the for loop:

for (int i = 1; i <= inputStr.length(); i++)
                  ^

or more readable:

for (int i = 0; i < inputStr.length(); i++) and ...subString(i, i + 1)

Upvotes: 0

Elliott Frisch
Elliott Frisch

Reputation: 201527

No String will .equals('a') a char. You could use .equals("a") but I'd prefer a for-each loop like

for(char ch : inputStr.toCharArray()){
    if (ch == 'a'){
        counterA++;
    }
}

Upvotes: 1

Scary Wombat
Scary Wombat

Reputation: 44854

substring is going to return a String not a char

so change to

if(inputStr.substring(i - 1, i).equals("a")){

Method one is better though.

Upvotes: 1

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