Trouble with Loop to Count Number of Given Characters in a String

Question

I have to use a provided loop to count the number of times the character 'b' appears in a String fourthString and for some reason it's returning an incorrect number. I believe it has to do with the if condition but I could be mistaken.

Any help would be HUGELY appreciated.

The string:

String fourthString = "a bat for baseball";

It should return 3.

The format for the code:

char target        ='b';                               
int  length        = fourthString.length( );               
int  count         = 0;                                
int  startNxtSrch  = 0;                                
int  foundAt       = 0;                               

while( ....... ) {
    foundAt = .......;
    if ( ....... ) {
        startNxtSrch = foundAt +1;
        count += 1;
    } else {
        startNxtSrch = length;
    }
}  
System.out.printf( "%nThere are %d occurrences of '%c' in fourthStr.%n", 
                   count,
                   target );

What I tried that is returning an incorrect number:

int i = 0;

while( i < length ) {
    foundAt = startNxtSrch;
    if ( fourthString.indexOf('b', startNxtSrch) != -1 ) {
        startNxtSrch = foundAt + 1;
        count += 1;
        i++;
    } else {
        startNxtSrch = length;
        i++;
    }
}
System.out.printf( "%nThere are %d occurrences of '%c' in fourthStr.%n", 
                   count,
                   target );

Possible duplicate of Java: How do I count the number of occurrences of a char in a String? — 1stthomas
– 1stthomas, Commented Nov 23, 2017 at 17:12
Thanks. I actually already reviewed this posting and it did not help as my problem has to fit a specific format and I believe the issue is related to the loop, not the counting of the characters hence the title. — CoolHand
– CoolHand, Commented Nov 23, 2017 at 17:17
Looks to me like the condition ought to be startNxtSrch < length. But I agree with some of the other comments: This is a very convoluted approach. And you probably should not add the i variable. I believe all the necessary variables are already present in the template. — Henrik Aasted Sørensen
– Henrik Aasted Sørensen, Commented Nov 23, 2017 at 17:20

Petter Friberg · Accepted Answer · 2017-11-23 19:59:22Z

2

This will give you the correct count of chars:

char target        = 'b';
int  length        = fourthString.length( );
int  count         = 0;
int  startNxtSrch  = 0;
int  foundAt       = 0;

while(startNxtSrch < length) {
    foundAt = fourthString.indexOf(target,startNxtSrch);
    if (foundAt>=0) {
        startNxtSrch = foundAt + 1;
        count += 1;
    } else {
        startNxtSrch = length;
    }
}
System.out.printf( "%nThere are %d occurrences of '%c' in fourthStr.%n",
            count,
            target );

edited Nov 23, 2017 at 19:59

Petter Friberg

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answered Nov 23, 2017 at 17:36

Safayat Rahaman

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Comments

Jimmy Fraiture · Accepted Answer · 2017-11-23 17:15:37Z

0

A better way to do it is to pass throught the whole array and count the number of time your char occured.

String fourthString = "a bat for baseball";
char target = 'b';
count = 0;
for(int i = 0; i < fourthString.length; i++){
    if(fourthString.charAt(i) == traget){
        count++;
    }
}
System.out.println(count);

answered Nov 23, 2017 at 17:15

Jimmy Fraiture

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1 Comment

CoolHand Over a year ago

Totally agree. However, I am not looking for a "better way" as I am required to follow the format provided. It's overly complicated but I can only change the ...... parts of the format provided.

Apostolis I. · Accepted Answer · 2017-11-23 17:30:29Z

0

You can use the following line of code:

int count = StringUtils.countMatches("the string you want to search in", "desired string");

For your example:

int count = StringUtils.countMatches("a bat for baseball", "b");

You can find a similar question and this answer here: https://stackoverflow.com/a/1816989/8434076

EDIT

while(startNxtSrch != lenth)
{
   foundAt = indexOf('b', startNxtSrch);
   if (foundAt != -1)
   {
      startNxtSrch = foundAt +1;
      count += 1;
   }  
   else
      startNxtSrch = length;
}

edited Nov 23, 2017 at 17:30

answered Nov 23, 2017 at 17:14

Apostolis I.

1126 bronze badges

2 Comments

CoolHand Over a year ago

I appreciate the feedback but the format has to follow what was provided and I can only change the ..... parts of the code. Seems overly complicated to me as well.

Apostolis I. Over a year ago

check my edited answer. i think that's what you are looking for :)

1stthomas · Accepted Answer · 2017-11-23 17:35:04Z

0

This, to me looks very complicated.

If I would write this code, here is a simpler solution:

while( i < length ) {
    if (fourthString.contains("b")) {
        fourthString = fourthString.replaceFirst("b", "");
        count++;
    }
    i++;
}

System.out.printf( "%nThere are %d occurrences of '%c' in fourthStr.%n",
                count,
                target );

edited Nov 23, 2017 at 17:35

1stthomas

1,0082 gold badges19 silver badges28 bronze badges

answered Nov 23, 2017 at 17:17

Safeer Ansari

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1 Comment

CoolHand Over a year ago

I agree, it's overly complicated but I am required to follow the format provided and only change the ..... parts of the code which is why I'm having so much trouble figuring it out.

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