Trying to convert an if-else statement to a switch statement but ending up with an error

all I've been trying to convert the following if statement into a switch statement.

/**
 * Return appropriate comment for given score and par for hole.
 * You can assume that score is not less than 4 below par for hole.
 * For example, if score is 4 below par, return "condor!!!!",
 * if score is 3 below par, return "albatross!!!",
 * if score is 2 below par, return "eagle!!", etc.
 * See Assign 2 description for full list of comments.
 * @param score
 * @param parForHole
 * @return appropriate comment for given score and par for hole.
 */
public static String comment(int score, int parForHole) {   
    if ( score == parForHole-4)
        return "condor!!!!";
    if ( score == parForHole-3)
        return "albatross!!!";
    if ( score == parForHole-2)
        return "eagle!!";
    if ( score == parForHole-1)
        return "birdie!";
    if ( score == parForHole)
        return "par";
    if ( score == parForHole+1)
        return "bogey";
    if ( score == parForHole+2)
        return "double bogey";
    if ( score == parForHole+3)
        return "triple bogey";

return "Not valid"; // Replace by a suitable switch stmt.
}

This was my attempt:

public static String comment(int score, int parForHole) {   

     String monthString;
        switch (score) {
            case parForHole-4:  monthString = "condor!!!!";
                     break;
            case parForHole-3:  monthString = "albatross!!!";
                     break;
            case parForHole-2:  monthString = "eagle!!";
                     break;
            case parForHole-1:  monthString = "birdie!";
                     break;
            case parForHole:  monthString = "par";
                     break;
            case parForHole+1:  monthString = "bogey";
                     break;
            case parForHole+2:  monthString = "double bogey";
                     break;
            case parForHole+3:  monthString = "triple bogey";
                     break;
            default: monthString = "Invalid";
                     break;
        }
        return monthString;

}

When I try to run this, eclipse gives me errors for each case condition that "case expressions must be constant expressions". I am not sure how to overcome this problem. Can anyone help me out? Thanks.