title: How to remove duplicate words in string without using array?
body: <p>Is there any way we can remove duplicate words from a String without using Arrays?</p>
  
  <p>For example, I have this sentence "<strong>this <em>is</em> java programming <em>program</em></strong>", 
  and the output have to be "<strong>this java programming</strong>".</p>
  
  <p>I see similar remove duplicate problems but all of them are using arrays.</p>