程序打印额外的 null 我似乎无法摆脱

Question

public class Student {
    
    private String courses = null;
    
    }
.....Some code here.......
    
    //Enroll in courses
    public void enroll() {
        //Get inside a loop and user hits Q
        do { 
            System.out.print("Enter Course to Enroll(Q to quit): ");
            Scanner in = new Scanner(System.in);
            String course = in.nextLine();
            if (!course.equals("Q")) {
                courses = courses + "\n " + course;
                tuitionBalance = tuitionBalance + costOfCourse;
            
            }
            else{ break; }      
        }while ( 1!= 0);

    }


......Some code here......
    
    //Show Status
    public String showInfo() {
        return "Name: " + firstName + " " + lastName + 
                "\nGrade level: " + gradeYear +
                "\nStudent ID: " + studentId +
                "\nCourses Enrolled:" + courses +
                "\nBalance: $" + tuitionBalance;
    }


}

Everything seems to be running just fine. But there's an extra null printed after the Courses Enrolled that sticks out like a sore thumb. How could I get rid of it? I've tried setting the String variable courses to null and also without assigning but doesn't seem to affect the result

Name: Frank Kuo
Grade level: 1
Student ID: 11001
Courses Enrolled:null
 Math101
Balance: $0

Answer 1

You can replace private String courses = null; with private String courses = ""; to get rid of the null .