在String中查找句子的开头

I want to display the results of a searchquery in a website with a title and a short description. The short description should be a small part of the page which holds the searchterm. What i want to do is: 1 strip tags in page 2 find first position of seachterm 3 from that position, going back find the beginning (if there is one) of that sentence. 4 Start at the found position in step 3 and display ie 200 characters from thereI want to display the results of a searchquery