Java关于+=赋值运算符的澄清

Question

我对 += 赋值运算符的工作原理有点困惑。我知道 x += 1 是 x = x+1。但是，在此代码中，有一个名为“字符串输出”的字符串变量，并使用空字符串进行初始化。我的困惑是变量“输出”有 5 个不同的输出，但我不知道它存储在哪里。帮忙澄清一下我的误解。我似乎无法弄清楚。

import java.util.Scanner;

public class SubtractionQuiz {
public static void main(String[] args) {
    final int NUMBER_OF_QUESTIONS = 5; //number of questions
    int correctCount = 0; // Count the number of correct answer
    int count = 0; // Count the number of questions
    long startTime = System.currentTimeMillis();
    String output = " "; // Output string is initially empty
    Scanner input = new Scanner(System.in);

    while (count < NUMBER_OF_QUESTIONS) {
        // 1. Generate two random single-digit integers
        int number1 = (int)(Math.random() * 10);
        int number2 = (int)(Math.random() * 10);

        // 2. if number1 < number2, swap number1 with number2
        if (number1 < number2) {
            int temp = number1;
            number1 = number2;
            number2 = temp;
        }

        // 3. Prompt the student to answer "What is number1 - number2?"
        System.out.print(
          "What is " + number1 + " - " + number2 + "? ");
        int answer = input.nextInt();

        // 4. Grade the answer and display the result
        if (number1 - number2 == answer) {
            System.out.println("You are correct!");
            correctCount++; // Increase the correct answer count
        }
        else
            System.out.println("Your answer is wrong.\n" + number1
                + " - " + number2 + " should be " + (number1 - number2));


        // Increase the question count
        count++;

        output +=  "\n" + number1 + "-" + number2 + "=" + answer +
                ((number1 - number2 == answer) ? " correct" : "        
                                    wrong");

    }

    long endTime = System.currentTimeMillis();
    long testTime = endTime = startTime;

    System.out.println("Correct count is " + correctCount +
      "\nTest time is " + testTime / 1000 + " seconds\n" + output);

    }


 }

Answer 1

Badshah 给出的答案对于您的程序来说是值得赞赏的，如果您想了解更多有关运算符(operator)可用性的信息，请查看我遇到的这个问题

+ operator for String in Java

发布的答案有很好的运营商推理