Using a while loop to count instances in a string in java

Question

Problem

How many instances of a certain character are there between the beginning of the string and a break point?

The break point is the first instance of another character.

For example, my string could be

hi, I need help! with this problem!

and I want to use a while loop to count the h s from the beginning to the !, so the output would be 2.

I am extremely new to java so I only know how to use a while loop to count up to a certain number but I don't know how to break or how to ask it to count just a certain character. Any hint in the right direction would be great.

My idea is to do something like:

while(character equals 'h', count)
else(don't count)
break if(character equals !)
print

But I don't know how to translate that to java

Your idea sounds right. Try it. Read tutorials about while loops, conditionals and variables. — Andy Turner
– Andy Turner, Commented Jan 30, 2016 at 20:22

ninja.coder · Accepted Answer · 2016-02-01 18:26:23Z

2

Here is a quick code snippet:

/**
 * Method Name: countChars
 * Arguments: 4 (Original String, Character to be found, Start Index, 
 *               Stop/Terminate Character)
 * Returns: Character Count
**/
public int countChars(String str, char c, int start, char e) {
     char[] chr = str.toCharArray();
     /* Initialize Count Counter */
     int count = 0;

     /* Initialize Counter With Start Index */
     int i = start;
     /* Iterate String For Positive Matches */
     while(i < chr.length) {
          /* Core Logic */
          if(chr[i] == e) {
               /* Terminate Character Found : Break Loop */
               break;
          } else if(chr[i] == c) {
               /* Match Found : Increment The Counter */
               count++;
          }
          /* Increment Loop Counter */
          ++i;
     }

     /* Return Character Count */
     return count;
}

You can call this method as follows:

int count = countChars(myString, 's', 0, '!');

edited Feb 1, 2016 at 18:26

answered Jan 30, 2016 at 20:23

ninja.coder

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6 Comments

Andy Turner Over a year ago

Code dumps without explanation are not helpful to a beginner. Please explain what you are doing in this code.

Andy Turner Over a year ago

Also, I don't think this quite does what is being asked - it should go to the first instance of "another character", not within a certain range.

ninja.coder Over a year ago

@Andy Thanks for your response. Added Comments & Changed the Terminate Condition.

Nick94107 Over a year ago

Those for loops makes sense to me and I've done some before. The book I'm working from specifically asks for a while loop though and to use a string variable, any way to do it that way?

ninja.coder Over a year ago

@Nick94107 Changed it to use while instead of for.

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