为什么我可以通过命令行插入记录时，为什么仅将.txt文件的最后一条记录插入到AVL树中？

问题描述

我正在一个需要一个.txt文件并读取记录列表并将其插入AVL树的项目中。似乎可以从文件中读取记录，但是只能将文件中的最后一条记录插入树中。还有一个命令行界面，允许用户将记录添加到树中。该接口可以正常工作并插入其他记录。这是.txt文件和代码的示例。

.txt file:
# Names for database
# Don't modify this file
# These are comments
# File description:
# ID,FirstName LastName Age
1 Aeris Lopez 18
2 Sofia Yeong 33

读取.txt文件并将其插入树中的方法：

public static void readRecords() throws FileNotFoundException {

        int idNumber = 0;
        String fName = "";
        String lName = "";
        String age = "";
        String line = "";

        Scanner inFile = new Scanner(new FileReader("test.txt"));

        inFile.nextLine();
        inFile.nextLine();
        inFile.nextLine();
        inFile.nextLine();
        inFile.nextLine();


        while (inFile.hasNext()) {

            idNumber = inFile.nextInt();
            record.setIdNumber(idNumber);

            fName = inFile.next();
            record.setfName(fName);

            lName = inFile.next();
            record.setlName(lName);

            if (inFile.hasNext())
            age = inFile.next();
            else
                age = "";
            record.setAge(age);

            tree.insert(record);
            System.out.println(record);
        }

        inFile.close();
    }

命令行用户界面方法：

public static void commands() {

//        commandList();

        Scanner console = new Scanner(system.in);
        Record record = new Record();
        int choice = console.nextInt();
        int idNumber;
        String age;
        int count = 0;
        String lName = "";
        String fName = "";


        switch (choice) {
            case 1: //Allows user to search for record by last name.
                System.out.println("Enter the last name to search for.\n");
                findLName = console.next();
//                AVLTree.findLastName(record);
                commands();
                break;

            case 2: //Allows user to search for record by first and last name.
                System.out.println("Enter the first and last name to search for.\n");
                findFName = console.next();
                findLName = console.next();

                commands();
                break;

            case 3: //Allows user to add a new record.
                System.out.println("Enter the id number,first name,last name,and age" +
                        "of the record to be added.\n");
                idNumber = console.nextInt();
                record.setIdNumber(idNumber);

                fName = console.next();
                record.setfName(fName);

                lName = console.next();
                record.setlName(lName);

                age = console.next();
                record.setAge(age);

                RecordUtils.tree.insert(record);
                System.out.println("Record #" + idNumber + " has been added.\n\n\n");
                RecordUtils.tree.printTree(AVLTree.root);

                commands();
                break;

            case 4: //Prints out the total number of records in the AVL tree.
                System.out.println("There are " + RecordUtils.tree.countNodes() + " records in The Amazo Name " +
                        "Storage Program Shadow Magic 2000 System\n\n\n");

                commands();
                break;

            case 5: //Prints out the user command list.
                commandList();
                commands();
                break;

            case 6: //Prints out the author of the code.
                System.out.println("This code was created by Toby Myers.\n\n\n");
                commands();
                break;

            case 7: //Allows the user to exit the program.
                System.out.println("Exiting The Amazo Name Storage Program " +
                        "Shadow Magic 2000 System.");
                System.exit(0);
                break;
            default: //Notifies user if invalid input is entered.
                System.out.println("Invalid Input");
                commands();
        }


    }

我很乐意提供更多其他信息。

谢谢！

解决方法

您的静态方法readRecords将信息添加到Record对象中，但是由于该对象不是在方法中创建的，因此您将在同一实例中为每一行覆盖信息。

解决方案是为每一行创建一个新对象

  while (inFile.hasNext()) {
        Record record = new Record(); //<-- This is needed

        idNumber = inFile.nextInt();
        record.setIdNumber(idNumber);

        fName = inFile.next();
        record.setfName(fName);

        lName = inFile.next();
        record.setlName(lName);

        if (inFile.hasNext())
        age = inFile.next();
        else
            age = "";
        record.setAge(age);

        tree.insert(record);
        System.out.println(record);
    }