/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.regex.*;
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		String rx = "(?<!#.{0,1000})\\btester\\b";
		Pattern pat = Pattern.compile(rx);
		String[] ss = new String[] {"tester, #tester","test tester # test tester","tester"};
		for (String s: ss){
		    Matcher matcher = pat.matcher(s);
	    	System.out.println(matcher.replaceAll("<em>$0</em>"));
		}
	}
}

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