java - 查找 primeNumber 和repDigit 失败

Question

我有一种方法可以判断一个数字是否是素数。它在我的测试类中工作，但是当我使用 System.outprintf 时，它失败了。与repDigit方法相同。

如有任何帮助，我们将不胜感激

求质数的方法:

/**
     * Checks whether the number is a prime number.
     *
     * @param number Any number
     * @return true if the number is prime, otherwise false
     */
    public static boolean isPrime(int number) {
        boolean isPrime = true;
        if (number < 2) {
            isPrime = false;
        } else {
            // Start counting from two to begin with even numbers
            for (int i = 2; i < number/2; ++i) {
                if (number % i == 0) {
                    isPrime = false;
                }
            }
        }
        return isPrime;
    }

查找repDigit的方法:

 /**
 * This method checks if numbers, after each other, are the same. We take
 * modulus of the number, in order to get the last digit, as long as the
 * number is above 0. The number is divided by 10, to end up with all
 * remaining numbers. Then it checks, if the last digit + the remaining are
 * the same
 *
 * @param number
 * @return
 */
public static boolean isRepDigit(int number) {
    int repDigit = number % 10;
    boolean toReturn = true;
    if (number < 10) {
        toReturn = false;
    } else {
        while (number > 0) {
            int digit = number % 10;
            number = number / 10;
            if (repDigit != digit) {
                toReturn = false;
            }
        }
    }
    return toReturn;
}

主要方法:

    public static void main(String[] args) {
    final int START = 5;
    final int END = 100;
    final int SPACE = digitCount(END);
    for (int i = START; i < END; i++) {

        System.out.printf("%" + SPACE + "d is a repdigit &n", isRepDigit(i));
        System.out.printf("%" + SPACE + "d is a prime &n", isPrime(i));
    }
}

错误消息:

Exception in thread "main" java.util.IllegalFormatConversionException: d != java.lang.Boolean
at java.util.Formatter$FormatSpecifier.failConversion(Formatter.java:4302)
at java.util.Formatter$FormatSpecifier.printInteger(Formatter.java:2793)
at java.util.Formatter$FormatSpecifier.print(Formatter.java:2747)
at java.util.Formatter.format(Formatter.java:2520)
at java.io.PrintStream.format(PrintStream.java:970)
at java.io.PrintStream.printf(PrintStream.java:871)
at Grp17_ueb01.main(Grp17_ueb01.java:164)
C:\Users\rasmu\Documents\NetBeansProjects\ueb01\nbproject\build-impl.xml:1040: The following error occurred while executing this line:
C:\Users\rasmu\Documents\NetBeansProjects\ueb01\nbproject\build-impl.xml:805: Java returned: 1
BUILD FAILED (total time: 1 second)

Answer 1

我认为您误解了printf第二个参数的含义。这里字符串中的 d 应该替换为小数，作为第二个参数给出。并且 boolean 值 isRepDigit(i) 无法转换为十进制。

可以找到 printf 方法文档 here .

格式字符串语法解释here .

我认为你想要的是:

    if (isRepDigit(i)) {
        System.out.printf("%" + SPACE + "d is a repdigit \n", i);
    }
    if (isPrime(i)) {
        System.out.printf("%" + SPACE + "d is a prime \n", i);
    }