package demo; import java.util.HashMap; import java.util.Scanner; public class exercise333 { private static Scanner scanner; /** * 学生信息集合 */ private static HashMap<String,Student> map; public static void main(String[] args) { // TODO Auto-generated method stub select(); } private static void select() { System.out.println("请输入学号："); Scanner sc = new Scanner(System.in); String nub = sc.nextLine(); Student student = map.get(nub); if(student == null) System.out.println("没有查询到该学生！"); else System.out.println(student.toString()); } } class Student{ private String sno; /** * 学号 */ private String name; /** * 姓名 */ private String major; /** * 专业 */ private String score; /** * 成绩 */ public String toString() { return "学生信息{"+ "学号='" + sno + '\'' + "姓名='" + name + '\'' + "专业='" + major + '\'' + "成绩='" + score + '\'' + '}'; } public String getSno() { return sno; } public void setSno(String sno) { this.sno = sno; } public String getName() { return name ; } public void setName(String name) { this.name = name; } public String getMajor() { return major; } public void setMajor(String major) { this.major = major; } public String getScore() { return score; } public void setScore(String score) { this.score =score; } public Student(String sno,String name,String major,String score) { this.sno = sno; this.name = name; this.major = major; this.score = score; } }

There are a few issues with the provided code:

1. The `map` object is not initialized, which will cause a `NullPointerException` when using the `get` method. To fix this, initialize the map object before using it:

private static HashMap<String,Student> map = new HashMap<String,Student>();

2. The `toString` method in the `Student` class is missing some plus signs to concatenate the strings. Fix it by adding the plus signs:

public String toString() {
    return "学生信息{" +
            "学号='" + sno + '\'' +
            ", 姓名='" + name + '\'' +
            ", 专业='" + major + '\'' +
            ", 成绩='" + score + '\'' +
            '}';
}

3. The `score` field is declared as `String`, which is not a suitable type for storing scores. Change it to a numeric type, such as `int` or `double`.

4. The `setScore` method has a typo and should be `this.score = score;`

5. It's a good practice to use `try-catch` blocks when reading from input, as the input could be incorrect and cause exceptions. For example, using `Integer.parseInt()` to get an integer from input could throw a `NumberFormatException`, and using `scanner.nextLine()` could throw a `NoSuchElementException` if there is no more input available.

Here is the fixed code with these issues addressed:

package demo;

import java.util.HashMap;
import java.util.Scanner;

public class Exercise333 {
    private static Scanner scanner;
    /** 学生信息集合 */
    private static HashMap<String, Student> map = new HashMap<String, Student>();

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        select();
    }

    private static void select() {
        System.out.println("请输入学号：");
        Scanner sc = new Scanner(System.in);
        String nub = sc.nextLine();

        try {
            Student student = map.get(nub);
            if (student == null)
                System.out.println("没有查询到该学生！");
            else
                System.out.println(student.toString());
        } catch (Exception e) {
            System.out.println("输入有误！");
        } finally {
            sc.close();
        }
    }
}

class Student {
    private String sno; /** 学号 */
    private String name; /** 姓名 */
    private String major; /** 专业 */
    private int score; /** 成绩 */

    public String toString() {
        return "学生信息{" +
                "学号='" + sno + '\'' +
                ", 姓名='" + name + '\'' +
                ", 专业='" + major + '\'' +
                ", 成绩='" + score + '\'' +
                '}';
    }

    public String getSno() {
        return sno;
    }

    public void setSno(String sno) {
        this.sno = sno;
    }

    public String getName() {
        return name;
    }

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

    public String getMajor() {
        return major;
    }

    public void setMajor(String major) {
        this.major = major;
    }

    public int getScore() {
        return score;
    }

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

    public Student(String sno, String name, String major, int score) {
        this.sno = sno;
        this.name = name;
        this.major = major;
        this.score = score;
    }
}