Question

我在java中工作，只要有用户指定的项目，我希望我的循环运行。截至目前，代码运行一次迭代，并读取一个循环的结果，但它不会再继续。

如果用户说有3个项目，我希望代码在循环中运行3次并告诉我每个项目的总数。现在，它告诉我1个项目的总数，我是否指定项目数是1或5.

    double projectBoardFootage = 1.0;
    double projectBoardFootageTotal = 0.0;
    int i = 0;

    System.out.println("How many projects do you want to estimate?");
    int numberOfProjects = scan.nextInt();


    for(i = 0; i < numberOfProjects; ++i) {
        while (projectBoardFootage > 0) {
            System.out.println("Enter your board footage for Project #" + (i + 1) + " (0 to exit)");
            projectBoardFootage = scan.nextDouble();
            projectBoardFootageTotal += projectBoardFootage;
        }
        System.out.println("The raw board footage for Project #" + (i + 1) + " is: " + projectBoardFootageTotal);
    }

Answer 1

您的代码中的问题是您使用变量projectBoardFootage来终止循环。想想当这个值设置为0时会发生什么。我们退出while循环，值永远不会再次更改。所以从那时起，每次迭代都会立即结束。

更好的解决方案是做这样的事情：

public static void main(String[] args)
{
    Scanner scan = new Scanner(System.in);
    System.out.println("How many projects do you want to estimate?");
    int numberOfProjects = scan.nextInt();

    for(int i = 0; i < numberOfProjects; ++i) {
        foobar(scan, i+1);
    }        
}

private static void foobar(Scanner scan, int projectNr)
{        
    boolean wantsToQuit = false;
    double projectBoardFootageTotal = 0;
    while (!wantsToQuit) {
        System.out.println("Enter your board footage for Project #" + projectNr + " (q to exit)");
        String tmp = scan.next();
        if(tmp.equalsIgnoreCase("q"))
           wantsToQuit = true;
        else
            projectBoardFootageTotal += Double.parseDouble(tmp);
    }
    System.out.println("The raw board footage for Project #" + projectNr + " is: " + projectBoardFootageTotal);        
}

此代码还可确保用户输入比＃0; 0＆＃39;更合理的密钥代码。退出。

Answer 2

也许您想重新初始化总的电路板素材以清除之前的迭代计数？

for(i = 0; i < numberOfProjects; ++i) {
    projectBoardFootageTotal = 0.0;
    while (projectBoardFootage > 0) {
        System.out.println("Enter your board footage for Project #" + (i + 1) + " (0 to exit)");
        projectBoardFootage = scan.nextDouble();
        projectBoardFootageTotal += projectBoardFootage;
    }
    System.out.println("The raw board footage for Project #" + (i + 1) + " is: " + projectBoardFootageTotal);
}

多个项目的Java循环

2 个答案: