java - 为什么我收到 "symbol not found"错误？

Question

我正在尝试编译我的主类，Halloween ，但我收到一个错误，指出该类 TreatHouse没有找到。我不确定为什么会发生这种情况，但是有人可以帮助我吗？另外，请随时评论您在我的代码中可能看到的任何其他错误；任何帮助是极大的赞赏。谢谢!

import java.util.ArrayList;
import java.util.Random;
import java.util.Scanner;

public class Halloween {

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        ArrayList<TreatHouse> houses = new ArrayList<TreatHouse>();

        Random gen = new Random(System.currentTimeMillis());
        int numHouse = gen.nextInt(10) + 1;

        // create houses
        for (int i = 0; i < numHouse; i++) {
            System.out.println("House " + i );
            System.out.println("Which candy should we give out first? Candy in pot 1 or candy in pot 2?");
            int candyPot = scan.nextInt();

            System.out.println("How much candy did we buy?");
            int totalCandy = scan.nextInt();

            houses.add( new TreatHouse(candyPot, totalCandy));
        }

        boolean allDone = false;
        while(!allDone){
            //Each house will pass out candy for a bit.
            for (TreatHouse house : houses) {
                house.passTime();               
            }

            //Check to see if all the house are done. If so set sentinel flag to true and exit while loop
            allDone = false;
            for(TreatHouse house: houses){
                //If a single house is not done then all are not done
                if(!house.isDone()){
                    allDone = false;
                    break;
                }
                else
                    allDone = true;
            }

            //Call static method to display some statistics about the holiday so far


        }
        System.out.println("All houses are done");
        scan.close();
    }
}

import java.util.Random;
import java.util.Scanner;

public class TreatHouse {
    private int candyPot1; // amount of candy in pot 1 for a single TreatHouse
    private int candyPot2; // amount of candy in pot 2 for a single TreatHouse
    private int currentPot; // (1 or 2) current Pot for a single TreatHouse
    private int totalCandy; // total candy for a single TreatHouse
    private int currentTreaters; // current Treaters for a single TreatHouse
    private boolean isDone = false; // is this house done for the night?
    private int treatsPerTreater; //How much candy to give out to each treater at a single TreatHouse
    private int nextID;

    //Static variables
    public static int participatingHouses = 0; //This contains the total number of houses participating in this year's holiday
    public static int totalCandyPassedOut = 0; //This contains the total number of candy passed out for all the houses.
    public static int totalTricksGiven = 0;    //This contains the total number of tricks given out. Remember that each kid gets tricked.
    public static int houseID = 1;              //This is the number for the house which is unique.

   //Constructor
   public TreatHouse()
   {
       participatingHouses++;
       totalCandyPassedOut++;
       totalTricksGiven++;
       nextID=houseID++;
   }      
    //Method to display the statistic variables
   public static void getHalloweenStatus()
   {
      System.out.println("Total participating houses: " + participatingHouses); //Displays the total number of participating houses
      System.out.println("Total candy passed out: " + totalCandyPassedOut);     //Displays the total amount of candy passed out 
      System.out.println("Total tricks given: " + totalTricksGiven);            //Displays the total amount of tricks given
      System.out.println(houseID);  
    }

    public TreatHouse(int candyPot, int totalCandy) {
        // Error Check and split candy
        if (totalCandy > 0) {
            candyPot1 = totalCandy / 2;
            candyPot2 = totalCandy / 2 + totalCandy % 2;
        } else {
            System.out.println("We can't give out candy if we don't have any."
                    + " I think we have some from last year. Yep, we have 100 " + "" + "pieces of candy to give out.");
            totalCandy = 100;
            candyPot1 = totalCandy / 2;
            candyPot2 = totalCandy / 2 + totalCandy % 2;
        }

        // currentPot Check
        if (candyPot == 1) {
            currentPot = 1;
        } else if (candyPot == 2) {
            currentPot = 2;
        } else {
            System.out.println("Invalid choice for pot. Only 1 or 2. Using pot 1");
            currentPot = 1;
        }

        //Adjust Static variables as needed here:


    }

    public void passTime() {
        Scanner scan = new Scanner(System.in);

        //before
        this.getCandyStatus();

        System.out.println("How much candy per treater should we give out?");
        this.setTreatsPerTreater(scan.nextInt());

        System.out.println("Knock, knock...." + "Trick or treat!");
        this.knockKnock();
        this.passOutCandy();

        //After
        this.getCandyStatus();

        //Determines if the house if done for the night.
        if(totalCandy == 0){
            System.out.println("Time to turn off the lights and go to bed!");
            System.out.println("The last candy came from pot number" + this.getLastPot());
            System.out.println("Happy Halloween!");
            isDone = true;
        }
    }

    private void printCurrentPot() {
        System.out.println("The current Pot is: " + currentPot);        
    }



    public int getCandyCount() {
        return candyPot1 + candyPot2;
    }

    public void passOutCandy() {
        // If there are enough treats per treater for the given amount per
        // treater, pass out candy from the current pot and switch to the other one.
        // Else display a message that the treaters have been tricked... (no
        // candy for them.) but do not change the current pot

        if ((currentPot == 1 && candyPot1 == 0) || (currentPot == 2 && candyPot2 == 0)) {
            // Switch pots and print message
            System.out.println("There is no candy in the currentPot Switching pots.");
            switchPots();
        }

        {// There is some candy to give out.
            int currentPotAmmount = getCurrentPotAmount();
            if (treatsPerTreater * currentTreaters <= currentPotAmmount) {
                //Passing out Candy
                if (currentPot == 1) {
                    candyPot1 -= treatsPerTreater * currentTreaters;
                    totalCandy -= treatsPerTreater * currentTreaters;
                } else {
                    candyPot2 -= treatsPerTreater * currentTreaters;
                    totalCandy -= treatsPerTreater * currentTreaters;
                }
                switchPots();
            } else {
                // trick
                System.out.println("You have been tricked!");
            }

        }

    }

    private int getCurrentPotAmount() {
        if (currentPot == 1)
            return candyPot1;
        else
            return candyPot2;
    }

    private void switchPots() {
        if (currentPot == 1) {
            currentPot = 2;
        } else
            currentPot = 1;

    }

    // Sets the number of trick or treaters.
    public void knockKnock() {
        Random gen = new Random(System.currentTimeMillis());
        this.currentTreaters = gen.nextInt(13) + 1; // 1 to 13 treaters.
        System.out.println("There are " + currentTreaters + " treaters.");
    }

    // Displays how much candy in each pot, total candy left

    public void getCandyStatus() {
        this.printCurrentPot();
        System.out.println("Candy in Pot 1: " + candyPot1);
        System.out.println("Candy in Pot 2: " + candyPot2);

    }

    // returns the pot number for which candy was last given.
    public int getLastPot() {
        if (currentPot == 1)
            return 2;
        else {
            return 1;
        }
    }

    public void setTreatsPerTreater(int treatsPerTreater) {
        this.treatsPerTreater = treatsPerTreater;
    }

    public boolean isDone() {

        return isDone;
    }
}

Answer 1

假设您将两个类(Halloween 和 TreatHouse)保存在不同的 java 文件中，如果 java 编译器无法找到类文件(在您的情况下 TreatHouse)，通常会出现“Symbol not find”异常

如果两个java文件在同一个文件夹中，那么当你编译Halloween.java时，它会自动编译TreatHouse.java，如果java文件在不同的文件夹中，你需要先编译TreatHouse.java并将类路径设置为TreatHouse。类位置稍后编译Halloween.java

或

如果您在同一个 java 文件中拥有这两个类，

从其中一个类中删除公共(public)访问修饰符，因为我们在一个java文件中只能有一个公共(public)类，并删除中间的导入语句并使用公共(public)类名保存文件

例如。

import java.util.ArrayList;
import java.util.Random;
import java.util.Scanner;
public class Halloween
{
//code
}

class TreatHouse
{
//code
}

上述代码的文件名应该是Halloween.java 编译Halloween.java(javacHalloween.java)后你会得到两个类文件Halloween.class和TreatHouse.class