java - 长类型输出文件

Question

我尝试创建一个文件并用 Java 将程序的输出写入其中。当我使用 WriteLong 时，文件不包含长值。请解释一下我如何创建这个文件。我的程序是打印 500000 和 10000000

之间的素数

public class primenumber {

    public static void main(String[] args) {

        long start = 5000000;
        long end = 10000000;
        System.out.println("List of prime numbers between " + start + " and " + end);
        for (long i = start; i <= end; i++) {
            if (isPrime(i)) {
                System.out.println(i);
            }
        }
    }

    public static boolean isPrime(long i2) {
        if (i2 <= 1) {
            return false;
        }
        for (long i = 2; i < Math.sqrt(i2); i++) {
            if (i2 % i == 0) {
                return false;
            }
        }
        return true;
    }
}

Answer 1

我假设您希望程序打印人类可读的 ASCII 长值。您可以使用 PrintWriter以及类似的东西，

PrintWriter pw = null;
try {
    pw = new PrintWriter(filePath);
    pw.println("List of prime numbers between " + start + " and " + end);
    for (long i = start; i <= end; i++) {
        if (isPrime(i)) {
            pw.println(i);
        }
    }
} catch (FileNotFoundException e) {
    e.printStackTrace();
} finally {
    pw.close();
}

或者，使用try-with-resources

try (PrintWriter pw = new PrintWriter(filePath)) {
    pw.println("List of prime numbers between " + start + " and " + end);
    for (long i = start; i <= end; i++) {
        if (isPrime(i)) {
            pw.println(i);
        }
    }
} catch (FileNotFoundException e) {
    e.printStackTrace();
}

如果你想创建一个二进制文件，你可以使用 DataOutputStream .