Look for a certain String inside another and count how many times it appears

Question

I am trying to search for a String inside a file content which I got into a String.

I've tried to use Pattern and Matcher, which worked for this case:

Pattern p = Pattern.compile("(</machine>)");
Matcher m = p.matcher(text);
while(m.find()) //if the text "(</machine>)" was found, enter
{
    Counter++;
}

return Counter;

Then, I tried to use the same code to find how many tags I have:

Pattern tagsP = Pattern.compile("(</");
Matcher tagsM = tagsP.matcher(text);
while(tagsM.find()) //if the text "(</" was found, enter
{
    CounterTags++;
}

return CounterTags;

which in this case, the return value was always 0.

Answer 1

Try using the below code , btw not using Pattern:-

String actualString = "hello hi how(</machine>) are you doing. Again hi (</machine>) friend (</machine>) hope you are (</machine>)doing good.";
//actualString which you get from file content
String toMatch = Pattern.quote("(</machine>)");// for coverting to regex literal
int count = actualString .split(toMatch, -1).length - 1; // split the actualString to array based on toMatch , so final match count should be -1 than array length.
System.out.println(count);

Output :- 4

Answer 2

You can use Apache commons-lang util library, there is a function countMatches exactly for you:

int count = StringUtils.countMatches(text, "substring");

Also this function is null-safe. I recommend you to explore Apache commons libraries, they provide a lot of useful common util methods.