如何返回到 while 循環的開頭？

Question

我只參加了一個月的編碼課程，所以如果我使用了一些錯誤/古怪的結構，我真的很抱歉。

我正在嘗試使用兩個隨機數制作加法游戲； r1確定加法問題中的項數，而r2為每個項分配一個值。 掃描器檢查用戶的輸入，並根據游戲給出分數或計算失敗的嘗試。

問題是第一次迭代運行良好，但它從不顯示新問題，即使尚未滿足主 while 循環的條件（3 個錯誤答案）。

你能給我一些指點嗎？ 謝謝！

import java.util.Random;
import java.util.Scanner;
import java.util.ArrayList;
public class AddingGame {
    Random rand1, rand2;
    int points = 0, wrong = 0, sum;
    String str = "";
    Scanner sc;
    ArrayList <Integer> mem;
    public AddingGame() {
        sc = new Scanner(System.in);
        rand1 = new Random();
        rand2 = new Random();
        int r1, r2, i;
        mem = new ArrayList <> ();
        System.out.println("Input any integer to receive a problem. Answer the problem correctly to proceed. Each correct answer yields a point. After three incorrect attempts, the game ends.");
        while (wrong <= 3) {
            mem.removeAll(mem);
            sum = 0;
            i = 0;
            str = "";
            
            r1 = rand1.nextInt(5) + 2; // determines the number of terms of a problem
            while (mem.size() <= (r1 - 1)) {
                r2 = rand2.nextInt(50) + 1; // determines the value of each term
                mem.add(r2);
                sum += r2;
                if (i == (r1 - 1)) {
                str = str + mem.get(i) + " = ?";
                } else {  
                str = str + mem.get(i) + " + "; 
                }  
                i++;
            }
            System.out.println(str);
            correct();
            while (sc.nextInt() != sum) {
                System.out.println("Try again!");
                System.out.println(str);
                wrong++;
                if (wrong == 3) {
                   System.out.println("You're out of attempts!");
                   break;
                }
                correct();
             }
        }
    }
    
    private void correct() {
        if (sc.nextInt() == sum) {
            points++;
            if (points != 1) {
                System.out.println("Correct! You now have " + points + " points!" );
            } else {
                System.out.println("Correct! You now have " + points + " point!" );
            }                
        }
    }
}

Answer 1

我想你可能想看看這個游戲的更簡單的實現，因為我注意到你正在努力弄清楚你需要哪些變量，哪些數據結構會有所幫助等等！

希望這能幫助你更好地理解如何用 Java 構建你的程序：

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

public class AddingGame {
    Random rand = new Random(); // no reason to have more than one instance of Random
    int points; // ints are automatically initialized to zero
    Scanner sc = new Scanner(System.in);

    public AddingGame() {
        System.out.println("Input any integer to receive a problem. Answer the problem correctly to proceed. Each correct answer yields a point. After three incorrect attempts, the game ends.");
        mainLoop:
        do { // keep playing until player gives up
            int sum = 0;
            String question = "";
            int termsCount = rand.nextInt(5) + 2; // determines the number of terms of a problem

            for (int i = 0; i < termsCount; i++) {
                int term = rand.nextInt(50) + 1; // determines the value of each term
                sum += term;
                if (i == termsCount - 1) { // this is the last term
                    question += term + " = ? ";
                } else {
                    question += term + " + ";
                }
            }
            System.out.print(question);
            int wrong = 0;
            while (!checkAnswerIsCorrect(sum)) {
                wrong++;
                if (wrong == 3) {
                    System.out.println("You're out of attempts!");
                    break mainLoop; // get out of mainLoop, not just the current one!
                }
                System.out.println("Try again!");
                System.out.print(question);
            }
        } while (shouldContinuePlaying());

        System.out.println("Total Points: " + points);
        System.out.println("GAME OVER!");
    }

    private boolean checkAnswerIsCorrect(int sum) {
        if (sc.nextInt() == sum) {
            points++;
            System.out.println("Correct! You now have " + points + " point" +
                    (points == 1 ? "" : "s") + "!");
            return true;
        }
        return false;
    }

    private boolean shouldContinuePlaying() {
        System.out.print("Continue playing? ");
        return sc.next().equals("yes");
    }

    public static void main(String[] args) {
        new AddingGame();
    }
}

我建議您在理解我的更改后將循環拆分為單獨的方法......這將使您更容易“專注於”游戲的單個部分，而不必在閱讀時將所有內容都記在腦海中代碼...我將大多數字段移至局部變量，因為在任何給定時間，范圍內只有少量事物（您可以“看到”的變量）總是更可取的 - 再次幫助程序員理解哪些值是重要的，並且可以/應該使用。

祝你好運，並希望你有一個偉大的程序員職業生涯。