如何通过用户输入字符串终止do-while循环？循环后代码未执行

你的循环无法终止的核心原因是do-while的终止条件逻辑错误：你把字符串数组dognames和字符串"quit"做相等比较，而数组和字符串是完全不同的对象，"quit".equals(dognames)永远返回false，导致!"quit".equals(dognames)永远为true，循环无限执行。

另外你的循环结构也存在问题：每次进入do块都会强制输入dogs条狗的信息，用户没有中途终止的机会，且输入完一轮后会重新开始输入，永远到不了后续的计算代码。

修正方案一：输入完一轮后询问是否继续循环 #

如果你的需求是先输入指定数量的狗的信息，再选择是否输入新一轮信息，可按以下方式修改：

import java.util.Scanner;

public class DogWeightCalculator {
    public static void main(String... args) {
        Scanner input = new Scanner(System.in);
        int dogs;

        System.out.println("How many dogs?");
        dogs = input.nextInt();

        String[] dognames = new String[dogs];
        Double[] dogweights = new Double[dogs];
        String continueInput;

        do {
            // 输入一轮狗的信息
            for (int i = 0; i < dogs; i++) {
                System.out.println("Enter dog name and weight: ");
                dognames[i] = input.next();
                dogweights[i] = input.nextDouble();
            }

            // 询问是否继续输入
            System.out.println("Enter 'quit' to stop, or any other key to continue:");
            continueInput = input.next();
        } while (!"quit".equals(continueInput)); // 用输入的字符串判断是否终止循环

        // 计算平均体重
        double sum = 0;
        for (double weight : dogweights) {
            sum += weight;
        }
        double dogweightsaverage = sum / dogweights.length;

        System.out.println("Average dog weight: " + dogweightsaverage);
        System.out.print("test");
    }
}

修正方案二：允许中途输入"quit"终止循环 #

如果想要在输入任意一条狗的信息时，输入"quit"直接终止整个流程，可修改为：

import java.util.Scanner;

public class DogWeightCalculator {
    public static void main(String... args) {
        Scanner input = new Scanner(System.in);
        int dogs;

        System.out.println("How many dogs?");
        dogs = input.nextInt();

        String[] dognames = new String[dogs];
        Double[] dogweights = new Double[dogs];
        boolean quit = false;

        for (int i = 0; i < dogs && !quit; i++) {
            System.out.println("Enter dog name and weight (or 'quit' to stop): ");
            String name = input.next();
            if ("quit".equals(name)) {
                quit = true;
                break;
            }
            dognames[i] = name;
            dogweights[i] = input.nextDouble();
        }

        // 未中途退出时才计算平均体重
        if (!quit) {
            double sum = 0;
            for (double weight : dogweights) {
                sum += weight;
            }
            double dogweightsaverage = sum / dogweights.length;

            System.out.println("Average dog weight: " + dogweightsaverage);
        }

        System.out.print("test");
    }
}

关键修正点总结 #

• 不要直接把数组和字符串做equals比较，需针对数组元素或单独的输入字符串判断终止条件
• 根据实际需求设计循环逻辑：要么一轮输入后询问是否继续，要么允许中途退出
• 循环终止后，后续的计算代码才能正常执行

内容的提问来源于stack exchange，提问作者Osprey