FooBarQix

import java.util.Map;
import java.util.TreeMap;

public class FooBarQix {

    // TreeMap sort key 3 > 5 > 7 for priority 
    private static final TreeMap<Integer, String> FOOBARQIX = new TreeMap<Integer, String>() {{
        put(7, "Qix");
        put(3, "Foo");
        put(5, "Bar");
    }};
    
    public static void main(String[] args) {
        
        // final result of algorithm
        String result = ""; 
        
        // current nbr in loop for traitement 
        String currentNbr;  
        
        for (int i=1; i<=100 ; i++) {
            currentNbr = null;
            // divisors first
            currentNbr = stringFromDiv(i); 
            currentNbr += stringFromNbr(i);
            
            // if current nbr has no divier and no numbre, we keep its value
            if(currentNbr.isEmpty()){ 
                currentNbr = String.valueOf(i);
            }
            result += currentNbr;
            result +="\n";
        }
        
        System.out.println(result);
        
    }
    
    private static String stringFromNbr(int nbr){
        StringBuilder out = new StringBuilder();
        // convert nbr to string and then to array character for replace char by char
        for(char c : String.valueOf(nbr).toCharArray()){
            // check if nbr is in FOOBARQIX
            if(FOOBARQIX.containsKey(Character.getNumericValue(c))){
                out.append(FOOBARQIX.get(Character.getNumericValue(c)));
            }
        }
        return out.toString();
    }
    
    private static String stringFromDiv(int nbr){
        StringBuilder out = new StringBuilder();
        // parse FOOBARQIX and we check if nbr has divider
        for(Map.Entry<Integer,String> entry : FOOBARQIX.entrySet()) {
            if(nbr % entry.getKey() == 0){
                out.append(entry.getValue());
            }
        }
        return out.toString();
    }
    
}