CODEWITHSUNDEEP
javastringsubstring
user3417853
user3417853

Reputation:

Count occurences of a substring in a string

im struggling to figure out where the error in my code is;

here is my test:

@Test
public void testCountOccurences()
{
    assertEquals(1, sc1.countOccurences("ence"));
    assertEquals(2, sc1.countOccurences("en"));
    assertEquals(1, sc2.countOccurences("that"));
    assertEquals(0, sc2.countOccurences("This"));
}

here is my method:

public int countOccurences(String t) 
{
    int j = 0;
    int i;
    for(i = 0; i < sentence.length(); i++)
    {
         String subString = sentence.substring(i, i + t.length());
         if(subString.equals(t))
            {
                j++;
            }
    }
    return j;
}

Upvotes: 2

Views: 152

Answers (3)

fge
fge

Reputation: 121712

You can use String.indexOf() for that:

public int countOccurrences(final String t)
{
    if (t == null || t.isEmpty())
        return 0;
    int index, startIndex = 0;
    int len = t.length();
    int ret = 0;

    while (true) {
        index = sentence.indexOf(t, startIndex);
        if (index == -1)
            break;
        startIndex = index + len;
        ret++;
    }

    return ret;
}

Upvotes: 1

Ted Bigham
Ted Bigham

Reputation: 4341

I'm betting your problem is i + t.length(). When 'i' is close to the length of your sentence, then i+t.length will be longer than the sentence, and you'll get an error.

Upvotes: 0

merlin2011
merlin2011

Reputation: 75545

I am going to assume that you're doing this as an exercise.

It seems that you are going off the end of the original string.

Try changing for(i = 0; i < sentence.length(); i++) to for(i = 0; i < sentence.length() - t.length(); i++).

Upvotes: 3

Related Questions