[JAVA] Non overlapping tagging of a sentence based on a dictionary of expressions

NonOverlappingTagging.java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;

/*
        Result is only one tagging of all the possible ones.
        The resulting tagging is determined by these two priority rules:
            - longest matches have higher priority
            - search is made from left to right
*/
public class NonOverlappingTagging {
	
	private static ArrayList non_overlapping_tagging(String[] sentence, HashMap dict,int max_key_size)
	{
		ArrayList tag_sentence = new ArrayList();
		int N = sentence.length;
	    if (max_key_size == -1)
	    {
	    	max_key_size = N;
	    }
	    int i = 0;
	    while (i < N)
	    {
	    	boolean tagged = false;
	    	int j = Math.min(i + max_key_size, N); //avoid overflow
	    	while (j > i)
	    	{
	    		String[] literal_tokens = Arrays.copyOfRange(sentence, i, j);
	    		String literal = join(literal_tokens, " ");
	    		System.out.println(literal);
	    		if (dict.get(literal) != null)
	    		{
	    			tag_sentence.add("["+literal+"]");
	                i = j;
	                tagged = true;
	    		}
	    		else
	    		{
	    			j -= 1;
	    		}
	    	}
	    	if (!tagged)
    		{
    			tag_sentence.add(sentence[i]);
	            i += 1;
    		}
	    }
	    return tag_sentence;
		
	}
	
	private static String join(String[] sentence, String separator)
	{
		String result = "";
		for (int i = 0; i < sentence.length; i++)
		{
			String word = sentence[i];
			result += word + separator;
		}
		return result.trim();
	}
	
	public static void main(String[] args) {
		String[] sentence = {"Los", "Angeles", "Lakers", "visited", "Washington", "State", "last", "week"};
		HashMap <String, Integer>dict = new HashMap();
		dict.put("Los Angeles", 1);
		dict.put("Lakers", 1);
		dict.put("Los Angeles Lakers", 1);
		dict.put("Washington", 1);
		dict.put("State", 1);
		dict.put("Washington State University", 1);
		
		ArrayList tagging = non_overlapping_tagging(sentence, dict, -1);
		
		System.out.println(tagging);	
	}
	
}