我的代码编译，但没有显示预期的输出。

Question

这是我的编程作业，它成功地编译，但是当我试图运行它时，输出看起来不像它应该做的那样。任何关于我所犯错误的建议都将不胜感激。谢谢

import java.util.Scanner;
/***********************************
 * Class: FRUnit5.java
 * Author: Robert Frankele
 *
 * Description: Ask user to enter the maximum random number of rounds (2-8).
 * Then ask the user how many rounds they would like to execute (1-8).
 * Display the results in formatted columns as follows:
 * (example using 8 as max random number, and 2 and number of rounds)
 *
 * Round    Rand #      Rand^Round      Modulus     Rand/Round
 *     1         7               7            0           7.00
 *     2         4              16            0           2.00
 */
public class FRUnit5
{

    public static void main(String[] args)
    {
        // Create a Scanner object for user input: 2pts
        Scanner userInput = new Scanner(System.in);
        // Variable to hold user's input for maximum random number: 2pts
        double maxRandNum;
        // Variable to hold the number of rounds the user wishes to execute: 2pts
        double numRound;
        double maxRound;

        // Variable to hold the random number generated from the Math class
        // using the user's maximum random number as an argument: 2pts
        double randNumMath;
        // Ask the user to enter the maximum random number to use (2-8): 2pts
        System.out.print("Enter the maximum random number to use ");
        // Store the number they entered into the variable declared above: 2pts
        maxRandNum = userInput.nextInt();
        // Clear the buffer
        userInput.nextLine();

        // Check to see if the number they entered is greater than 8: 5pts
        // If it is, display an error message and assign 8 as the maximum random number (see project example): 3pts
        // Then, assign 8 to the variable declared above that will hold the maximum random number: 3pts
            if (maxRandNum > 8)
        {
            System.out.println("The maximum random number has to be <= 8");
            maxRandNum = 8;
        }

        // Ask the user to enter the number of rounds they wish to execute.: 2pts
        System.out.print("Enter the number of rounds you wish to execute ");
        // Store the number they entered into the variable declared above: 2pts
        numRound = userInput.nextInt();

        // Print the header of the output, using the printf method: 8pts
        // Round    Rand #      Rand^Round      Modulus     Rand/Round
        System.out.printf("%10s%10s%15s%12s%15s\n", "Round", "Rand #", "Rand^Round", "Modulus", "Rand/Round");

        // Set up a for loop to iterate through the number of rounds: 10pts

        maxRound = 9;
        for (numRound = 0; numRound < maxRound; numRound++)
        {
            // Calculate the random number given the maximum random number, and store in a local variable called randomNum: 5pts
            int randomNum = (int) (Math.random() * maxRandNum + 1);


            // Calculate the Rand^Round number, using Math.pow(randomNum, round) as the equation,
            // and store in a local variable called randToRound: 5pts
            double randToRound = (Math.pow(randomNum, numRound));

            // Calculate the modulus: randomNum % round, and store in a variable called modulusOfRand: 3pts
            double modulusOfRand = randomNum % numRound;

            // Calculate randomNum / round and store in a variable called randDivRound: 3pts
            double randDivRound = randomNum / numRound;

            // Using printf, display the results, remembering to only display randDivRound with two places after the decimal point: 10pts
            System.out.printf("%10d%10d%15d%12d%15.2f\n", numRound, randomNum, randToRound, modulusOfRand, randDivRound);

        }

    } // end of main
} // end of class

这就是我所看到的:输入使用9的最大随机数--最大随机数必须是<= 8，输入希望执行6轮Rand #Rand^ rounds / Round在线程"main“中的<=8:d != java.lang.Double at java.util.Formatter$FormatSpecifier.printInteger(Formatter.java:2793) at java.util.Formatter$FormatSpecifier。在java.util.Formatter.format(Formatter.java:2520) at java.io.PrintStream.format(PrintStream.java:970) at java.io.PrintStream.printf(PrintStream.java:871) at FRUnit5.main(FRUnit5.java:76)按任意键继续。。。

Answer 1

看来你得到了一个java.util.IllegalFormatConversionException。

对于类型为%f的变量，请确保在printf()中使用的是%d而不是%d，因为%d与Java中的十进制整数一起使用。

改变这一点：

System.out.printf("%10d%10d%15d%12d%15.2f\n", numRound, randomNum, randToRound, modulusOfRand, randDivRound);

对此：

System.out.printf("%10f%10d%15f%12f%15.2f\n", numRound, randomNum, randToRound, modulusOfRand, randDivRound);

Answer 2

程序失败的原因是System.out.printf()方法中的格式。您已经将变量randToRound、modulusOfRand定义为double，但您正在尝试通过在格式化程序中使用%10d将它们格式化为int。

请添加System.out.print()以检查变量的值，并在System.out.printf()中添加适当的格式，这将解决您的问题。

可能的解决办法：

System.out.printf("%10d%10d%15d%12d%15.2f\n", (int)numRound, randomNum, (int)randToRound, (int)modulusOfRand,
                    randDivRound);

另外，numRound的循环应该从1开始，循环通过numRound当前逻辑运行9次，这不是问题语句中所期望的。