Java 只能从一个类访问当前Hashmap

所以你们现在可能都厌倦了我的问题。但是我被深深地困住了。我有一个calendar类、一个calendar tester类和一个event类。我在calendar类中有一个HashMap，我将事件类中的内容放入其中。问题是，只有事件类有它的信息。如果我试图从存储HashMap的类或tester类访问/打印HashMap，我会得到一个空的HashMap。我似乎已经在标有讨厌*的事件类中指出了问题所在。但我不知道如何继续，也不知道为什么这会影响我的其他两门课，但这门课不会。有人有什么想法吗

MyCalendarTester.java

import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.Scanner;
import java.util.Map.Entry;

enum MONTHS
{
    January, February, March, April, May, June, July, August, September, October, November, December;
}
enum DAYS
{
    Su, Mo, Tu, We, Th, Fr, Sa;
}

public class MyCalendarTester {

    static MONTHS[] arrayOfMonths = MONTHS.values();
    static DAYS[] arrayOfDays = DAYS.values();
    static MyCalendar myCal = new MyCalendar();
    static Event myEvent = new Event(null, null, null);

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        GregorianCalendar cal = new GregorianCalendar(); // capture today
        printCalendar(cal);
        menuHandler();

        System.out.println("\nI think we're done here!");
    }

    public static void  printCalendar(Calendar cal){

        GregorianCalendar dayCounter = new GregorianCalendar(); // capture today
        dayCounter.set(Calendar.DAY_OF_MONTH, 1);

        int formatCounter = 0;

        System.out.println("    " + arrayOfMonths[cal.get(Calendar.MONTH) ] + " " + cal.get(Calendar.YEAR)); //prints the month and year

        for(int i = 0; i < arrayOfDays.length; i++){
            if(i == 0){
                System.out.print(arrayOfDays[i]);
            }
            else{
                System.out.print(" " + arrayOfDays[i]);
            }
        }//print days of week

        System.out.println();
        for(int i = 0; i < arrayOfDays.length; i++){
            if(!arrayOfDays[i].equals(arrayOfDays[dayCounter.get(Calendar.DAY_OF_WEEK) - 1])){
                System.out.print("   ");
                formatCounter++;
            }
            else{
                System.out.print(" " + cal.getActualMinimum(Calendar.DAY_OF_MONTH) + " ");
                formatCounter++;
                break;
            }
        }

        for(int i = 1; i < cal.getMaximum(Calendar.DAY_OF_MONTH); i++){
            if(formatCounter == 7){
                System.out.println();
                formatCounter = 0; //reset counter
            }
            dayCounter.roll(Calendar.DAY_OF_MONTH, true);
            if(dayCounter.get(Calendar.DATE) == cal.get(Calendar.DATE)){
                System.out.print("[" + dayCounter.get(Calendar.DATE) + "]");
                formatCounter++;
            }
            else if(dayCounter.get(Calendar.DATE) <= 9){
                System.out.print(" " + dayCounter.get(Calendar.DATE) + " ");
                formatCounter++;
            }
            else{
                System.out.print(dayCounter.get(Calendar.DATE) + " ");
                formatCounter++;
            }


        }
    }

public static void menuHandler(){

Scanner sc = new Scanner(System.in);


System.out.println("\nSelect one of the following options:");
System.out.println("[L]oad [V]iew by [C]reate [G]o to [E]vent list [D]elete [Q]uit");

        char userChoice = sc.next().charAt(0);
        switch(Character.toUpperCase(userChoice)){
            case 'L':

            case 'V': 
                     myCal.viewCalendar();
                     menuHandler();

            case 'C':
                     myEvent.createEvent();
                        System.out.println("Here is what is in the HashMap103:");   
                        System.out.println("HashMap size = " + myCal.getMyCalHash().size());
                        for (Entry<GregorianCalendar, Event> entry : myCal.getMyCalHash().entrySet()) {
                            Event value = entry.getValue();
                            System.out.println("key, " + entry.getKey().get(Calendar.MONTH) + "/" + entry.getKey().get(Calendar.DATE) + "/" + entry.getKey().get(Calendar.YEAR) + 
                                    " value: " + value.eventName + " " + value.startTime.get(Calendar.HOUR_OF_DAY) + ":" + 
                                    value.startTime.get(Calendar.MINUTE) + " " + value.endTime.get(Calendar.HOUR_OF_DAY) + ":" + value.endTime.get(Calendar.MINUTE));
                          }
                     menuHandler();

            case 'G':
                    myEvent.goTo();
                    menuHandler();
            case 'E':
                    myEvent.eventList();
                    menuHandler();

            case 'D':
                    myEvent.deleteEvent();
                    menuHandler();

            case 'Q': return;
        }


    }

}

MyCalendar.java

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.HashMap;
import java.util.Scanner;
import java.util.Map.Entry;


public class MyCalendar {

    GregorianCalendar calendar = new GregorianCalendar();
    private HashMap<GregorianCalendar, Event> myCalHash = new HashMap<GregorianCalendar, Event>();
    GregorianCalendar dayCounter = new GregorianCalendar(); // capture today
    Scanner sc = new Scanner(System.in);
    static MONTHS[] arrayOfMonths = MONTHS.values();
    static DAYS[] arrayOfDays = DAYS.values();

    MyCalendar(){
        System.out.println("myCalendar()!!");
    }

    public HashMap<GregorianCalendar, Event> getMyCalHash(){
        System.out.println("myCalHash.size()23 = " + myCalHash.size());
        return myCalHash;
    }

    public void setMyCalHash(HashMap<GregorianCalendar, Event> myCalHash) {
        this.myCalHash = myCalHash;
    }

    public void viewCalendar() {
        System.out.println("myCalHash.size() = " + myCalHash.size()); // 0
            System.out.print("[D]ay view or [M]view? ");
            char userChoice = sc.next().charAt(0);
            if(Character.toUpperCase(userChoice) == 'D'){ dayView(); }
            else if(Character.toUpperCase(userChoice) == 'M'){ monthView(); }
            else{
                System.out.println("Invalid choice.");
            }
    }   

        public void dayView(){
            //print day calendar
            //GregorianCalendar dayCounter = new GregorianCalendar(); // capture today
            System.out.println("myCalHash.size() = " + myCalHash.size()); // 0
            System.out.println(arrayOfDays[calendar.get(Calendar.DAY_OF_WEEK) - 1] + ", " +  arrayOfMonths[calendar.get(Calendar.MONTH)] 
                    + " " + calendar.get(Calendar.DATE) + ", " + calendar.get(Calendar.YEAR));
            System.out.print("[P]revious or [N]ext or [M]ain menu ? ");
            char userChoice = sc.next().charAt(0);
            if(Character.toUpperCase(userChoice) == 'P'){
                calendar.add(Calendar.DAY_OF_MONTH, -1);
                dayView();
            }
            else if(Character.toUpperCase(userChoice) == 'N'){
                calendar.add(Calendar.DAY_OF_MONTH, 1);
                dayView();
            }
            else if(Character.toUpperCase(userChoice) == 'M'){
                return;
            }
            else{
                System.out.println("Invalid choice.");
                return;
            }
        }
        public void monthView(){
            //print month calendar
            int formatCounter = 0;
            System.out.println("myCalHash.size() = " + myCalHash.size()); // 0
            dayCounter.set(Calendar.DAY_OF_MONTH, 1);

            System.out.println("    " + arrayOfMonths[calendar.get(Calendar.MONTH) ] + " " + calendar.get(Calendar.YEAR)); //prints the month and year

            for(int i = 0; i < arrayOfDays.length; i++){
                if(i == 0){
                    System.out.print(arrayOfDays[i]);
                }
                else{
                    System.out.print(" " + arrayOfDays[i]);
                }
            }//print days of week

            System.out.println();
            for(int i = 0; i < arrayOfDays.length; i++){
                if(!arrayOfDays[i].equals(arrayOfDays[dayCounter.get(Calendar.DAY_OF_WEEK) - 1])){
                    System.out.print("   ");
                    formatCounter++;
                }
                else{
                    System.out.print(" " + calendar.getActualMinimum(Calendar.DAY_OF_MONTH) + " ");
                    formatCounter++;
                    break;
                }
            }

            for(int i = 1; i < dayCounter.getActualMaximum(Calendar.DAY_OF_MONTH); i++){
                if(formatCounter == 7){
                    System.out.println();
                    formatCounter = 0; //reset counter
                }
                dayCounter.roll(Calendar.DAY_OF_MONTH, true);
                if(dayCounter.get(Calendar.DATE) <= 9){
                    System.out.print(" " + dayCounter.get(Calendar.DATE) + " ");
                    formatCounter++;
                }
                else{
                    System.out.print(dayCounter.get(Calendar.DATE) + " ");
                    formatCounter++;
                }


            }

            System.out.print("\n[P]revious or [N]ext or [M]ain menu ? ");
            char userChoice = sc.next().charAt(0);
            if(Character.toUpperCase(userChoice) == 'P'){
                calendar.add(Calendar.MONTH, -1);
                dayCounter.add(Calendar.MONTH, -1);
                monthView();
            }
            else if(Character.toUpperCase(userChoice) == 'N'){
                calendar.add(Calendar.MONTH, 1);
                dayCounter.add(Calendar.MONTH, 1);
                monthView();
            }
            else if(Character.toUpperCase(userChoice) == 'M'){
                return;
            }
            else{
                System.out.println("Invalid choice.");
                return;
            }
        }


}

Event.java

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.HashMap;
import java.util.Map.Entry;
import java.util.Scanner;


public class Event {

    String eventName;
    GregorianCalendar startTime;
    GregorianCalendar endTime;

    MyCalendar mCal = new MyCalendar();

    Event(String eventName, GregorianCalendar startTime, GregorianCalendar endTime){
        this.eventName = eventName;
        this.startTime = startTime;
        this.endTime = endTime;
    } //end Event Constructor

    public void createEvent(){

        Scanner sc = new Scanner(System.in);
        System.out.print("Enter the name of the event: ");
        String name = sc.nextLine();
        System.out.print("Date of event: ");
        String dateAsString = sc.nextLine();
        String startTime = null;
        String endTime = null;
        GregorianCalendar calDate = new GregorianCalendar();
        String[] dateArr = dateAsString.split("/");
           calDate.set(GregorianCalendar.YEAR, Integer.parseInt(dateArr[2]));
           calDate.set(GregorianCalendar.MONTH, Integer.parseInt(dateArr[0]));
           calDate.set(GregorianCalendar.DATE, Integer.parseInt(dateArr[1]));

        System.out.print("Enter starting time and ending time(24 hour format, comma separated):");
        String times = sc.nextLine();
        // checks if user entered both start and end time
        if(times.contains(",")){
            String[] time = times.split(",");
            startTime = time[0];
            endTime = time[1];

            GregorianCalendar calSTime = new GregorianCalendar();
            String[] sTime = startTime.split(":");
            calSTime.set(Calendar.HOUR_OF_DAY, Integer.parseInt(sTime[0]));
            calSTime.set(Calendar.MINUTE, Integer.parseInt(sTime[1]));


            GregorianCalendar calETime = new GregorianCalendar();
            String[] eTime = endTime.split(":");
            calETime.set(Calendar.HOUR_OF_DAY, Integer.parseInt(eTime[0]));
            calETime.set(Calendar.MINUTE, Integer.parseInt(eTime[1]));

            //*********************
            Event myEvent = new Event(name, calSTime, calETime); // causing a new instance of myCalendar???
            //*********************

            mCal.getMyCalHash().put(calDate,  myEvent); //adding date and event to HashMap

        }else{ //if user did not specify an event end time
            startTime = times;
            endTime = null;

            GregorianCalendar calSTime = new GregorianCalendar();
            String[] sTime = startTime.split(":");
            calSTime.set(Calendar.HOUR_OF_DAY, Integer.parseInt(sTime[0]));
            calSTime.set(Calendar.MINUTE, Integer.parseInt(sTime[1]));
            Event myEvent = new Event(name, calSTime, null);
            mCal.getMyCalHash().put(calDate,  myEvent);//adding date and event to HashMap
        }

    System.out.println("Here is what is in the HashMap73:");    
    System.out.println("HashMap size = " + mCal.getMyCalHash().size());
    for (Entry<GregorianCalendar, Event> entry : mCal.getMyCalHash().entrySet()) {
        Event value = entry.getValue();
        System.out.println("key, " + entry.getKey().get(Calendar.MONTH) + "/" + entry.getKey().get(Calendar.DATE) + "/" + entry.getKey().get(Calendar.YEAR) + 
                " value: " + value.eventName + " " + value.startTime.get(Calendar.HOUR_OF_DAY) + ":" + 
                value.startTime.get(Calendar.MINUTE) + " " + value.endTime.get(Calendar.HOUR_OF_DAY) + ":" + value.endTime.get(Calendar.MINUTE));
      }



    }

    public void deleteEvent(){
        Scanner sc = new Scanner(System.in);
        System.out.println("[S]elected or [A]ll ?");
        char userChoice = sc.next().charAt(0);
        if(Character.toUpperCase(userChoice) == 'S'){ 
            //delete all events on the day
            Scanner nsc = new Scanner(System.in);
            System.out.println("Enter the date: ");

            String deleteDate = nsc.nextLine();

                String[] parsed = deleteDate.split("/");
                System.out.println("Integer.parseInt(parsed[0] = " + Integer.parseInt(parsed[0]));

                System.out.println("Integer.parseInt(parsed[1] = " + Integer.parseInt(parsed[1]));


                System.out.println("Integer.parseInt(parsed[2] = " + Integer.parseInt(parsed[2]));

                for (Entry<GregorianCalendar, Event> entry : mCal.getMyCalHash().entrySet()) {
                    System.out.println("entry.getKey().get(Calendar.MONTH) = " + entry.getKey().get(Calendar.MONTH));
                    System.out.println("entry.getKey().get(Calendar.DATE) = " + entry.getKey().get(Calendar.DATE));
                    System.out.println("entry.getKey().get(Calendar.YEAR) = " + entry.getKey().get(Calendar.YEAR));
                    if(entry.getKey().get(Calendar.MONTH) == Integer.parseInt(parsed[0]) 
                            && entry.getKey().get(Calendar.DATE) == Integer.parseInt(parsed[1]) 
                            && entry.getKey().get(Calendar.YEAR) == Integer.parseInt(parsed[2]) ){
                                mCal.getMyCalHash().remove(entry.getKey());
                                System.out.println("HashMap size = " + mCal.getMyCalHash().size());
                    }

                }

        }
        else if(Character.toUpperCase(userChoice) == 'A'){ 
            mCal.getMyCalHash().clear();
            System.out.println("HashMap size = " + mCal.getMyCalHash().size());
        }
        else{
            System.out.println("Invalid choice.");
        }
    }

    public void eventList(){
        if(mCal.getMyCalHash().equals(null)){
            System.out.println("Your calendar is empty!");
        }
        else{
            System.out.println("Here are your events: ");
            for (Entry<GregorianCalendar, Event> entry : mCal.getMyCalHash().entrySet()) {
                Event value = entry.getValue();

                System.out.println(value.eventName + " " + value.startTime.get(Calendar.HOUR_OF_DAY) + ":" + 
                        value.startTime.get(Calendar.MINUTE) + " " + value.endTime.get(Calendar.HOUR_OF_DAY) 
                        + ":" + value.endTime.get(Calendar.MINUTE));
            }
        }

    }


    public void goTo(){
        System.out.print("Enter a date in MM/DD/YYYY format: ");
        Scanner sc = new Scanner(System.in);
        String userDate = sc.nextLine();
        String[] dateArr = userDate.split("/");
          // dayCounter.set(GregorianCalendar.YEAR, Integer.parseInt(dateArr[2]));
        //   dayCounter.set(GregorianCalendar.MONTH, Integer.parseInt(dateArr[0]) - 1);
        //   dayCounter.set(GregorianCalendar.DATE, Integer.parseInt(dateArr[1]));

         //  System.out.println(arrayOfDays[dayCounter.get(Calendar.DAY_OF_WEEK) - 1] + ", " +  
        //   arrayOfMonths[dayCounter.get(Calendar.MONTH)] + " " + dayCounter.get(Calendar.DATE) + ", " + dayCounter.get(Calendar.YEAR));

           for (Entry<GregorianCalendar, Event> entry : mCal.getMyCalHash().entrySet()) {
//             System.out.println("entry.getKey().get(Calendar.MONTH) = " + entry.getKey().get(Calendar.MONTH));
//             System.out.println("Integer.parseInt(dateArr[0]) = " + Integer.parseInt(dateArr[0]));
//             System.out.println("entry.getKey().get(Calendar.DATE) = " + entry.getKey().get(Calendar.DATE));
//             System.out.println("Integer.parseInt(dateArr[1]) = " + Integer.parseInt(dateArr[1]) );
                if(entry.getKey().get(Calendar.MONTH) == Integer.parseInt(dateArr[0]) 
                        && entry.getKey().get(Calendar.DATE) == Integer.parseInt(dateArr[1]) 
                        && entry.getKey().get(Calendar.YEAR) == Integer.parseInt(dateArr[2]) ){
                    Event value = entry.getValue();

                    System.out.println(value.eventName + " " + value.startTime.get(Calendar.HOUR_OF_DAY) + ":" + 
                            value.startTime.get(Calendar.MINUTE) + " " + value.endTime.get(Calendar.HOUR_OF_DAY) 
                            + ":" + value.endTime.get(Calendar.MINUTE));

                }
           }

    }
}

---

我不确定我的提问方式是否符合论坛规则，所以如果我做错了什么，请告诉我。但是我想不出更好的方法来说明这一点，而不将我所有的代码都转储进去。

您是否尝试过并逐步浏览您的代码？像这样的工具将帮助您直接发现问题。您的****已走上正确的轨道。对于您的程序，您只需要有一个calendar实例，否则，尽管调用了相同的东西，最终还是会得到calendar类的多个实例。试着想想数据存储在哪里，并确保每个组件都使用相同的对象。@aurora91当然。每个事件对象都有一个MyCalendar实例，MyCalendarTester对象也是如此。调用myEvent.createEvent时会发生什么？那项新活动放在哪里？它被放在myEvent的MyCalendar中，而不是MyCalendarTester的MyCalendar中，这有意义吗？@aurora91这很正常，尽管还有其他方法可以做到。MyCalendarTester可以在创建它的MyCalendar实例时将其传递给事件，而不是执行您正在执行的操作，这样您就可以引用它。不过你做的很好。太棒了，非常感谢你的帮助，你帮了很多忙！！