String concatenation with nested if else statements

I'm currently reviewing for a test. Would anyone be able to tell me what is wrong with my code? It is for problem 5E. Don't understand why this won't run. "Finally, write a modified version of the code from the previous exercise, 5.(D)"

 public static void main(String[] args) 
    {
     int i = 12;
     int j = 10; 
     int m = 14;
     int n = 6;
     int numComparisons = 0;
     String comparisons = null;

     System.out.print("Madam");
     numComparisons++;
     comparisons =  comparisons + i + " < " + j;
     if (i < j)
     { 
     comparisons = comparisons + "? (T),";
     numComparisons++;
     if (m != n) 
     {
     comparisons = comparisons + m + "!=" + n  + "? (T),";
     System.out.print("How");
     }
     else
     {
     comparisons + m + "!=" + n  + "? (F),";
     System.out.print("Now");
     }
     }   
     System.out.print("I’m");
     numComparisons++;
     if (i >= m)
     {
     comparisons = comparisons + i + " >= " + m + "? (T),";
     System.out.println("Cow");
     }
     else
     { 
     comparisons = comparisons + i + " >= " + m + "? (T),";
     System.out.println("Adam"); 
     System.out.println("Number of comparisons: " + numComparisons);
     }
    System.out.println(comparisons);
    }
}