java - 在二叉搜索树中声明学生名册时出现 ExceptionInInitialize 错误

Question

我正在努力初始化包含学生的二叉搜索树名册。我试图首先将学生添加到名册中，但似乎无法让名册正常工作。我还创建了自己的 BST 类，而不是使用 java.utils。我将在下面发布我的所有代码。如何正确初始化我的名册 BST 以添加学生？

编译后出错:

run:
java.lang.ExceptionInInitializerError
Caused by: java.lang.RuntimeException: Uncompilable source code - Erroneous 
tree type: roster.BST
at Roster.Roster.<init>(Roster.java:152)
at Roster.Roster_Test.<clinit>(Roster.java:6)
 Exception in thread "main"
 BUILD FAILED (total time: 0 seconds)

编译后我的错误发生在以下行:

名册.类(class):

  BST rost = new BST();

以及上面的主要方法:

  static Roster rost = new Roster();

主类:

package roster;
import java.util.LinkedList;

public class Roster_Test {

static Roster rost = new Roster();

public static void main(String[] args) {

    addStudent();
    displayAllStudents();
    /*lookupStudent("11114");
    addCourse();
    displayStudents("Math161");
    displayCourses("11112");
    getCourseAverage("Math161");
    dropCoursesBelow("11114", 65);
    getCourseAverage("Math161");
    dropCourse("11111", "Math161");
    getCourseAverage("Math161");
    changeGrade("11112", "Math161", 80);
    getCourseAverage("Math161");*/

}

// add students to the roster
static void addStudent() {
    rost.addStudent(new Student("11111", "Jon", "Benson"));
    rost.addStudent(new Student("11112", "Erick", "Hooper"));
    rost.addStudent(new Student("11113", "Sam", "Shultz"));
    rost.addStudent(new Student("11114", "Trent", "Black"));
    rost.addStudent(new Student("11115", "Michell", "Waters"));
    rost.addStudent(new Student("11116", "Kevin", "Johnson"));
}

// display all students in the roster
static void displayAllStudents() {
    //rost.inOrder();
}

// lookup a student in the roster
static void lookupStudent(String id) {
    if (rost.find(id) != null) {
        System.out.println(id + " found");
    } else {
        System.out.println(id + " not found");
    }
}

// add courses to the roster
static void addCourse() {
    rost.addCourse("11111", new Course("CS116", 80));
    rost.addCourse("11111", new Course("Math161", 90));
    rost.addCourse("11112", new Course("Math161", 70));
    rost.addCourse("11112", new Course("CS146", 90));
    rost.addCourse("11112", new Course("CS105", 85));
    rost.addCourse("11113", new Course("CS216", 90));
    rost.addCourse("11114", new Course("CIS255", 75));
    rost.addCourse("11114", new Course("CS216", 80));
    rost.addCourse("11114", new Course("Math161", 60));
    rost.addCourse("11114", new Course("COMM105", 90));
}

// display students enrolled in a given course id
static void displayStudents(String courseId) {
    rost.displayStudents(courseId);
}

// display courses taken by a student
static void displayCourses(String id) {
    rost.displayCourses("id");
}

// display the average grade for a student
static void getCourseAverage(String courseId) {
    rost.getCourseAverage(courseId);
}

// display the average grade for a student
static void dropCoursesBelow(String id, int grade) {
    rost.dropCoursesBelow(id, grade);
}

// drop a course from a student
static void dropCourse(String id, String courseId) {
    rost.dropCourse(id, courseId);
}

// change the grade for a student
static void changeGrade(String id, String courseId, int grade) {
    rost.changeGrade(id, courseId, grade);
}

}

学生.类(class)

class Student implements Comparable <Student> {
String id;
String firstName;
String lastName;

Student(String id, String fName, String lName) {
    this.id = id;
    this.firstName = fName;
    this.lastName = lName;
}

public String getName() {
    return lastName;
}

public void setName(String lName) {
    this.lastName = lName;
}

public int compareTo(Student st) {
    int lastName = this.lastName.compareTo(st.getName());

    if (lastName > 0) {
        return 1;
    } else if (lastName < 0) {
        return -1;
    } else {
        return 0;
    }
}

public void addCourse(String id) {
    LinkedList list = new LinkedList();
    list.add(id);        
}

}

类(class).class:

class Course {
    String id;  // course id
    int grade;

Course(String id, int grade) {
    this.id = id;
    this.grade = grade;
}

}

名册.类(class):

class Roster {
    Student root;
    int numStudents;

    BST rost = new BST();

public Roster() {
    root = null;
    numStudents = 0;
}

public void addStudent(Student st) {
    rost.insert(st);
    numStudents++;
}

}

BST.java

package roster;

class BinarySearchTree<E extends Comparable<E>> {

private Node<E> root;

public BinarySearchTree() {
    root = null;
}

// Generic find method
public Node find(E e) {
    Node<E> current = root;

    // Loop until e.compare to current element is not equal to 0
    while (e.compareTo(current.element) != 0) {
        // if e.compare is less than 0 set current to current.left
        if (e.compareTo(current.element) < 0) {
            current = current.left;
        } // else if current is 0 or greater than 0 set current 
        // to current.right
        else {
            current = current.right;
        }
        // if current is null, return null
        if (current == null) {
            return null;
        }
    }
    // return current value when loop ends
    return current;
}

// Check whether the generic value was found and return true or false
public boolean findTF(E e) {

    // if find(e) returns a value return true
    // else return false if value was not found
    if (find(e) != null) {
        return true;
    } else {
        return false;
    }

}

public void insert(E e) {
    Node<E> newNode = new Node<>(e);

    if (root == null) {
        root = newNode;
    } else {
        Node<E> current = root;
        Node<E> parent = null;

        while (true) {
            parent = current;
            if (e.compareTo(current.element) < 0) {
                current = current.left;
                if (current == null) {
                    parent.left = newNode;
                    return;
                }
            } else {
                current = current.right;
                // if current is equal to null,
                // set parent.right to newNode and return
                if (current == null) {
                    parent.right = newNode;
                    return;
                }
            }
        }
    }
}

public void traverse(int traverseType) {
    switch (traverseType) {
        case 1:
            System.out.print("\nPreorder traversal: ");
            // call preOrder(root) and implement preOrder()
            preOrder(root);
            break;
        case 2:
            System.out.print("\nInorder traversal:  ");
            inOrder(root);
            break;
        case 3:
            System.out.print("\nPostorder traversal: ");
            // call postOrder(root) and implement postOrder()
            postOrder(root);
            break;
    }
    System.out.println();
}

// Recursive method - traverse generic BST 
// While root is not equal to null visit left node and print value
// of root, then visit right node. Repeat until root becomes null
private void inOrder(Node<E> localRoot) {
    if (localRoot != null) {
        inOrder(localRoot.left);
        System.out.print(localRoot.element + " ");
        inOrder(localRoot.right);
    }
}

// Recursive method - traverse generic BST 
// While root is not equal to null print the value of the root
// and visit left then right nodes. Repeat until root becomes null
private void preOrder(Node<E> localRoot) {
    if (localRoot != null) {
        System.out.print(localRoot.element + " ");
        preOrder(localRoot.left);
        preOrder(localRoot.right);
    }
}

// Recursive method - traverse generic BST 
// While root is not equal to null visit left node and visit
// the right node and print value of root. Repeat until root becomes null
private void postOrder(Node<E> localRoot) {
    if (localRoot != null) {
        postOrder(localRoot.left);
        postOrder(localRoot.right);
        System.out.print(localRoot.element + " ");
    }
}

}

class Node<E> {

protected E element;
protected Node<E> left;
protected Node<E> right;

public Node(E e) {
    element = e;
}
}

Answer 1

由于错误Caused by: java.lang.RuntimeException: Uncompilable source code - Erroneous tree type: roster.BST 指示 -

您正在运行的代码中，一个/多个 java 文件尚未成功或正确编译。

我看到的一件事是，您正在使用 BST rost = new BST();，但您没有任何名为 BST 的类。不应该是 BinarySearchTree rost = new BinarySearchTree () 吗？

随后，清理/删除所有旧的类文件重新编译并尝试。