Question

伙计们，我一直在努力弄清楚为什么这段代码将近5个小时都没有显示出适当的结果！这应该是一个非常容易的任务，但它使我发疯。我必须使该项目能够使用包含的代码而不是其他类似的代码。我的问题是没有在软件底部显示质数。根据我的理解，此代码应显示质数1-100，并且所有数均由5个数字组成，最后一个数字除外。一些指导非常感谢。

public class Prime numbers 1-100{
public static void main (String[] args) {

    int number = 100;

    // Assume the number is prime
    boolean isPrime = true; // Is the current number prime?

    // Test if number is prime
    for (int divisor = 2; divisor <= number / 2; divisor++) {
        if (number % divisor == 0) { // If true, number is not prime
            isPrime = false; // Set isPrime to false
            break; // Exit for loop
        }
        // print prime numbers
        if(isPrime)
            System.out.println("Prime numbers between 1 and " + number);
    }
}

}

Answer 1

您的代码应具有嵌套循环和一个数组，该数组存储找到的质数显示在末尾。

要在最后打印它们，您应该先打印您的语句，然后使用循环来打印包含找到的素数的数组。

Answer 2

如果要打印从1到100的所有质数，则必须遍历所有这些数字（第一个循环），并且对于每个质数都遍历所有可能的除数（嵌套循环）：

int number = 100;

boolean isPrime = false;

System.out.println("2");
System.out.println("3");

for (int i = 5; i <= number; i++) {
    for (int divisor = 2; divisor <= Math.sqrt(i); divisor++) {
        isPrime = !(i % divisor == 0);
        if (!isPrime)
            break;
    }

    if (isPrime)
        System.out.println("" + i);
}

注意，对于2和3条件无法应用，因此先打印它们。
我使用了@selbie的优化提示<= sqrt(number)

Answer 3

public class Prime{
public static void main (String[] args) {
    boolean isPrime = true; 
    // iterate over all numbers from 1 to 100
    for (int number = 1; number <= 100; number++) {
        // We want to believe it's a prime
        isPrime = true;
        // 1 is not a prime
        if (number == 1) isPrime = false;
        // iterate over all numbers which are lower then 'number'
        for (int divisor = 2; divisor < number && isPrime; divisor++) {
            // if we can divide by it, it's not a prime
            if (number % divisor == 0) {
                isPrime = false;
            }
        }
        // print if it's a prime
        if (isPrime) System.out.println(number+", ");
    }
}}

Answer 4

我要感谢大家的建议和技巧。和推动我的动力。我能够使该程序正常工作。见下文

public class primes {
public static void main (String[] args) {
    final int NUMBER_OF_PRIMES = 26; // Number of primes to display
    final int NUMBER_OF_PRIMES_PER_LINE = 5; // Display 5 numbers per line
    int count = 0; // Count the number of prime numbers
    int number = 1; // A number to be tested for primeness

    System.out.println("The prime numbers between 1 and 100 are \n");

    // Repeatedly find prime numbers
    while (count < NUMBER_OF_PRIMES) {
        // Assume the number is prime
        boolean isPrime = true; // Is the current number prime?

        // Test whether number is prime
        for (int divisor = 2; divisor <= number / 2; divisor++) {
            if (number % divisor == 0) { // If true, number is not prime
                isPrime = false; // Set isPrime to false
                break; // Exit the for loop
            }
        }

        // Display the prime number and increase the count
        if (isPrime) {
            count++; // Increase the count

            if (count % NUMBER_OF_PRIMES_PER_LINE == 0) {
                // Display the number and advance to the new line
                System.out.println(number);
            }
            else
                System.out.print(number + " ");     
            }

        //Check if the next number is prime
        number++;
        }
    }
}

Java中1到100之间的质数

4 个答案: