Java determines whether a number is prime [goto]

http://blog.csdn.net/lwcumt/article/details/8027586

Import Java.util.Scanner;

prime number, also known as Prime , refers to the number of natural numbers greater than 1 , except 1 and this integer itself, cannot be divisible by other natural numbers

public class Primenumber {

public static void Main (string[] args) {

Scanner scan = new Scanner (system.in);// scanner, receiving console input information

System.out.print (" Please enter an integer:");

try {

int num = Scan.nextint ();// Remove information from console input

if (IsPrime (num)) {// call isprime () method

SYSTEM.OUT.PRINTLN (num + " is a prime number!) ");// if the isprime () method returns true, the output is a prime number

} else {

SYSTEM.OUT.PRINTLN (num + " is not a prime number!) ");// if the isprime () method returns false, the output is not a prime number

}

} catch (Exception e) {

System.out.println (" Please enter an integer ");// Catch an exception, if the input is not an integer, the output exception

}

}

/**

* <pre>

* used to determine if a number is a prime, if it is prime, returns true, otherwise false

* </pre>

*

* @param a

* the value entered

* @return True,false

*/

public static Boolean isprime (int a) {

Boolean flag = true;

if (a < 2) {// primes not less than 2

return false;

} else {

for (int i = 2; I <= math.sqrt (a); i++) {

If (a% i = = 0) {// if divisible, the description is not a prime, return false

Flag = false;

break;// Jump out of the loop

}

}

}

return flag;

}

}

Java determines whether a number is prime [goto]