Java 当我进入这个项目时，我对#2和#3的选择将不起作用。有人能帮我理解它为什么会这样吗？
当我进入这个项目时，我对#2和#3的选择将不起作用。我可以选择选项1，输入数据，构建地图，然后退出并正确显示地图。但当我试图删除或编辑学生/成绩时，它将不起作用。有人能帮我理解它为什么会这样吗？由于我是java的noob，我也愿意听取关于如何改进代码的建议Java 当我进入这个项目时，我对#2和#3的选择将不起作用。有人能帮我理解它为什么会这样吗？,java,Java,当我进入这个项目时，我对#2和#3的选择将不起作用。我可以选择选项1，输入数据，构建地图，然后退出并正确显示地图。但当我试图删除或编辑学生/成绩时，它将不起作用。有人能帮我理解它为什么会这样吗？由于我是java的noob，我也愿意听取关于如何改进代码的建议 import java.util.*; public class StudentGrades { public static void main(String[] args) { // TODO Auto-gene
import java.util.*;
public class StudentGrades {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner in = new Scanner(System.in);
Choices choice = new Choices();
final String WELCOME = "Welcome to the student and grade registry." + "\n" + "Choose from your options below: " + "\n" + "1: Add Students" + "\n" + "2: Remove Students" + "\n" + "3: Modify Grades" + "\n" + "4: Print All Grades" + "\n" + "5: Exit the System";
int selection;
boolean sent = true;
while (sent != false){
System.out.println(WELCOME);
selection = in.nextInt();
if (selection == 5){
sent = false;
}
else if (selection == 1){
choice.addStudent();
}
else if (selection == 2){
choice.removeStudent();
}
else if (selection == 3){
choice.editGrade();
}
else if (selection == 4){
choice.printAll();
}
else{
System.out.println("You have chosen an incorrect selection, please try again.");
}
}
}
}
class Choices implements Comparator<Choices> {
Scanner in = new Scanner(System.in);
Map<String, String> map = new TreeMap<String, String>();
final String STUDENT = "Please enter a student: ";
final String GRADE = "Please enter a grade: ";
final String ENTRY = "You have chosen to enter new students. " + "\n" + "To exit data entry at any time press 'e'. ";
final String REMOVE = "You have chosen to remove students. " + "\n" + "To exit data entry at any time press 'e'. ";
final String REM_MESS = "You have chosen to remove ";
final String REM_MESS2 = " with grade average of ";
final String GRADE_EDIT = "You have chosen to edit grades. " + "\n" + "To exit data entry at any time press 'e'. ";
boolean sent = false;
String student;
String grade;
public int compare(Choices a, Choices b){
return a.toString().compareToIgnoreCase(b.toString());
}
public void addStudent(){
while (sent != true){
System.out.println(ENTRY);
System.out.println(STUDENT);
student = in.nextLine();
if (student.equals("e")){
sent = true;
break;
}
System.out.println(GRADE);
grade = in.nextLine();
if (student.equals("e")){
sent = true;
break;
}
map.put(student, grade);
}
}
public void removeStudent(){
while (sent != true){
System.out.println(REMOVE);
System.out.println(STUDENT);
student = in.nextLine();
if (student.equals("e")){
sent = true;
break;
}
else {
System.out.println(REM_MESS + student + REM_MESS2 + map.get(student));
map.remove(student);
}
}
}
public void editGrade(){
while (sent != true){
System.out.println(GRADE_EDIT);
System.out.println(STUDENT);
student = in.nextLine();
if (student.equals("e")){
sent = true;
break;
}
else {
System.out.println(student);
System.out.println(GRADE);
grade = in.nextLine();
map.put(student, grade);
}
}
}
public void printAll(){
for (String key : map.keySet()){
String name = map.get(key);
System.out.println(key + ": " + name);
}
}
}
好吧，我有点累了，但我已经尽我所能让你的代码正常工作了（如果我遗漏了什么，请告诉我）：
import java.util.*；
公营班级学生成绩{
公共静态void main（字符串[]args）{
//TODO自动生成的方法存根
扫描仪输入=新扫描仪（系统输入）；
选择=新的选择（）；
最后一个字符串WELCOME=“欢迎使用学生和成绩注册表。”+“\n”+”从下面的选项中选择：“+”\n”+“1:添加学生”+“\n”+“2:删除学生”+“\n”+“3:修改成绩”+“\n”+“4:打印所有成绩”+“\n”+“5:退出系统”；
int选择；
布尔循环=真；
while（循环==true）{
System.out.println（欢迎）；
请尝试{selection=in.nextInt（）；}
catch（异常e）{System.out.println（e.toString（））；break；}
如果（选择==5）{
循环=假；
}else if（选择==1）{
choice.addStudent（）；
}else if（选择==2）{
choice.removeStudent（）；
}else if（选择==3）{
choice.editGrade（）；
}else if（选择==4）{
choice.printAll（）；
}否则{
System.out.println（“您选择的选项不正确，请重试。”）；
}
}
}
}
类选择实现了Comparator{
扫描仪输入=新扫描仪（系统输入）；
Map Map=newtreemap（）；
最后一个字符串STUDENT=“请输入学生：”；
final String GRADE=“请输入等级：”；
final String ENTRY=“您已选择输入新学员。”+“\n”+”要随时退出数据输入，请按“e”；
final String REMOVE=“您已选择删除学生。”+“\n”+”要随时退出数据输入，请按“e”；
最后一个字符串REM_MESS=“您已选择删除”；
最终字符串REM_MESS2=“平均等级为”；
final String GRADE_EDIT=“您已选择编辑成绩。”+“\n”+”要随时退出数据输入，请按“e”；
布尔循环=真；
弦乐学生；
串级；
公共整数比较（选项a、选项b）{
返回a.toString（）.compareToIgnoreCase（b.toString（））；
}
公共图书馆（学生）{
while（循环==true）{
系统输出打印项次（输入）；
系统输出打印（学生）；
student=in.nextLine（）；
如果（学生等于（e）{
循环=真；
打破
}
系统输出打印项次（等级）；
等级=in.nextLine（）；
如果（学生等于（e）{
循环=真；
打破
}
地图。放置（学生、年级）；
}
}
公共无效再投资（）{
while（循环==true）{
系统输出打印项次（删除）；
系统输出打印（学生）；
student=in.nextLine（）；
如果（学生等于（e）{
循环=真；
打破
}否则{
System.out.println（REM_MESS+student+REM_MESS2+map.get（student））；
地图。移除（学生）；
}
}
}
公共职系（）{
while（循环==true）{
系统输出打印LN（等级编辑）；
系统输出打印（学生）；
student=in.nextLine（）；
如果（学生等于（e）{
循环=真；
打破
}否则{
系统输出打印（学生）；
系统输出打印项次（等级）；
等级=in.nextLine（）；
地图。放置（学生、年级）；
}
}
}
public void printAll（）{
for（字符串键：map.keySet（））{
字符串名称=map.get（键）；
System.out.println（键+“：”+名称）；
}
}
}
编辑：顺便说一下
中断和loop=false
是冗余的。考虑选择一个而不是两者。我会试试你的代码，但是你能把你的问题缩小到更少的来源吗？肖恩，我不确定你的意思。每个单独的方法都独立工作，因为如果我先尝试每个方法，它将正常运行。当我试着返回并选择第二个选项时，它不起作用。肖恩，我支持这个令人厌倦的评论，哈哈。它仍然在做同样的事情。如果选择选项1，添加一些学生和分数，退出，然后选择选项2。我只是一遍又一遍地得到主方法菜单。我没有考虑try/catch短语，我很欣赏循环布尔语句的编辑。@user3424867我所做的是添加一个用户，输入e进入主循环，然后删除一个用户，最后再次输入e退出删除循环。我将再次尝试代码，看看还能找到什么：）我试图显示我看到的内容，但它没有正确显示。谢谢你的帮助。我使用了loop=false和break；最初是因为选项1。如果我在询问学生时只使用选项1中的loop=false，它仍然会询问分数，所以我想打破它，所以我找到了答案。我删除了loop=false，只使用break；它成功了。知道为什么吗？
Welcome to the student and grade registry.
Choose from your options below:
1: Add Students
2: Remove Students
3: Modify Grades
4: Print All Grades
5: Exit the System
1
You have chosen to enter new students.
To exit data entry at any time press 'e'.
Please enter a student:
Tom
Please enter a grade:
B
You have chosen to enter new students.
To exit data entry at any time press 'e'.
Please enter a student:
e
Welcome to the student and grade registry.
Choose from your options below:
1: Add Students
2: Remove Students
3: Modify Grades
4: Print All Grades
5: Exit the System
2
Welcome to the student and grade registry.
Choose from your options below:
1: Add Students
2: Remove Students
3: Modify Grades
4: Print All Grades
5: Exit the System
2
Welcome to the student and grade registry.
Choose from your options below:
1: Add Students
2: Remove Students
3: Modify Grades
4: Print All Grades
5: Exit the System
import java.util.*;
public class StudentGrades {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner in = new Scanner(System.in);
Choices choice = new Choices();
final String WELCOME = "Welcome to the student and grade registry." + "\n" + "Choose from your options below: " + "\n" + "1: Add Students" + "\n" + "2: Remove Students" + "\n" + "3: Modify Grades" + "\n" + "4: Print All Grades" + "\n" + "5: Exit the System";
int selection;
boolean loop = true;
while (loop == true) {
System.out.println(WELCOME);
try { selection = in.nextInt(); }
catch (Exception e) { System.out.println(e.toString()); break; }
if (selection == 5) {
loop = false;
} else if (selection == 1) {
choice.addStudent();
} else if (selection == 2) {
choice.removeStudent();
} else if (selection == 3) {
choice.editGrade();
} else if (selection == 4) {
choice.printAll();
} else {
System.out.println("You have chosen an incorrect selection, please try again.");
}
}
}
}
class Choices implements Comparator<Choices> {
Scanner in = new Scanner(System.in);
Map<String, String> map = new TreeMap<String, String>();
final String STUDENT = "Please enter a student: ";
final String GRADE = "Please enter a grade: ";
final String ENTRY = "You have chosen to enter new students. " + "\n" + "To exit data entry at any time press 'e'. ";
final String REMOVE = "You have chosen to remove students. " + "\n" + "To exit data entry at any time press 'e'. ";
final String REM_MESS = "You have chosen to remove ";
final String REM_MESS2 = " with grade average of ";
final String GRADE_EDIT = "You have chosen to edit grades. " + "\n" + "To exit data entry at any time press 'e'. ";
boolean loop = true;
String student;
String grade;
public int compare(Choices a, Choices b) {
return a.toString().compareToIgnoreCase(b.toString());
}
public void addStudent() {
while (loop == true) {
System.out.println(ENTRY);
System.out.println(STUDENT);
student = in.nextLine();
if (student.equals("e")) {
loop = true;
break;
}
System.out.println(GRADE);
grade = in.nextLine();
if (student.equals("e")) {
loop = true;
break;
}
map.put(student, grade);
}
}
public void removeStudent() {
while (loop == true) {
System.out.println(REMOVE);
System.out.println(STUDENT);
student = in.nextLine();
if (student.equals("e")) {
loop = true;
break;
} else {
System.out.println(REM_MESS + student + REM_MESS2 + map.get(student));
map.remove(student);
}
}
}
public void editGrade() {
while (loop == true) {
System.out.println(GRADE_EDIT);
System.out.println(STUDENT);
student = in.nextLine();
if (student.equals("e")) {
loop = true;
break;
} else {
System.out.println(student);
System.out.println(GRADE);
grade = in.nextLine();
map.put(student, grade);
}
}
}
public void printAll() {
for (String key : map.keySet()) {
String name = map.get(key);
System.out.println(key + ": " + name);
}
}
}