カプセル化の学習をしていますが、思うようにコードが動きません。

package lesson10_7;

public class Grade {
private String name;
private int score;
//private String grade;

public Grade(String name,int score) {
    this.name = name;
    this.score = score;
//  this.grade=null;
}

public String getName() {
    return name;
}
public int getScore() {
    return score;
}
//public String getGrade() {
////    return grade;
//}
public void setName() {
    this.name = name;
}

public void setScore() {
    this.score = score;
}

//public void judge() {
//    if(90<score) {
//      this.grade = "AA";
//    } else if(80<score) {
//      this.grade = "A";
//    } else if(70<score) {
//      this.grade = "B";
//    } else if(60<score) {
//      this.grade = "C";
//    }
//}

//public String judge() {
//if(90<score) {
//  this.grade = "AA";
//  return grade;
//} else if(80<score) {
//  this.grade = "A";
//  return grade;
//} else if(70<score) {
//  this.grade = "B";
//  return grade;
//} else if(60<score) {
//  this.grade = "C";
//  return grade;
//}
//}
public String judge() {
    String a = null;
    if(90<score) {
        a="AA";
 //       return "AA";
    }else if(80<score) {
        a="A";
        return "A";
    } else if(70<score) {
        a="B";
//      return "B";
    } else if(60<score) {
        a="C";
//      return "C";
    }
    return a;
}


 public static void main(String[] args) {
    Grade n1= new Grade("伊藤",60);
//  Grade n2= new Grade("鈴木",88);
//  Grade n3= new Grade("佐藤",40);
//  Grade n4= new Grade("中山",74);
//  Grade n5= new Grade("池田",95);
//  Grade n6= new Grade("池山",80);
    n1.judge();

    System.out.println(n1.getName() +  ":" + n1.judge());


}

}