java - toStrings() 的堆栈溢出错误 (java)

Question

我的两个 toString() 似乎处于无限循环中，但我不确定问题出在哪里。我已经调试了几个小时，看不出有什么问题。

对于上下文，主要的相关部分是: System.out.println(class1); adminStaff1.assignInstructor(class1, instructor1); System.out.println(class1);

第一个 println 有效，但是当我调试时，我在它通过之前看到一个源查找错误。第二个 class1 创建 StackOverflowError 是:

Exception in thread "main" java.lang.StackOverflowError
at java.lang.AbstractStringBuilder.append(Unknown Source)
at java.lang.StringBuilder.append(Unknown Source)
at java.lang.StringBuilder.<init>(Unknown Source)
at Instructor.toString(Instructor.java:59)
at java.lang.String.valueOf(Unknown Source)
at java.lang.StringBuilder.append(Unknown Source)
at Class.toString(Class.java:89)
at java.lang.String.valueOf(Unknown Source)
at java.lang.StringBuilder.append(Unknown Source)
at java.util.AbstractCollection.toString(Unknown Source)
at java.lang.String.valueOf(Unknown Source)
at java.lang.StringBuilder.append(Unknown Source)
at Instructor.toString(Instructor.java:59)

类的 toString 是:

@Override
public String toString() {
    return "Class [instructor=" + instructor + ", lectureHall="
            + lectureHall + ", currentEnrollment=" + currentEnrollment
            + ", timeSlot=" + timeSlot + ", filled=" + filled
            + ", studentList=" + studentList + "]";
}

Instructor 的 toString 是:

@Override
public String toString() {
    return "Instructor [salary=" + salary + ", classList=" + classList
            + ", openTimeSlots=" + openTimeSlots + ", "
            + super.toString() + "]";
}

super.toString() 是:

@Override
public String toString() {
    return "[idNumber=" + idNumber + ", email=" + email
            + "]";
}

我不确定为什么，但 adminStaff1.assignInstructor 似乎也导致了这个问题，它是:

public void enrollStudent(Student student, Class aClass){
    aClass.checkIfFilled();
    if(!aClass.getFilled()){
        aClass.addStudent(student);
        student.addClass(aClass);
        aClass.increaseEnrollment();
    } else {
        System.out.println("Could not add student because the class is currently full.");
    }
}

如果有人能帮助我理解问题所在，我将不胜感激。谢谢。

Answer 1

当您在 Class 上调用 toString() 时，它包括 Instructor(而 Instructor 包括类)。这是一个循环。打破它，要么

return "Instructor [salary=" + salary + /* ", classList=" + classList */
        + ", openTimeSlots=" + openTimeSlots + ", "
        + super.toString() + "]";

或者，

return "Class [lectureHall=" + lectureHall + ", currentEnrollment=" 
        + currentEnrollment + ", timeSlot=" + timeSlot + ", filled=" + filled
        + ", studentList=" + studentList + "]";