Question

用 java 怎么判断一个数是否为质数？

Answer 1

质数：　

public static boolean isPrime(int N){if( N < 2 ) return false;

for( int i = 2 ; i*i <= N; i++){if( N % i == 0) return false;return true;}

JAVA 编程方法：

public static void main(String[] args) {// TODO Auto-generated method stub
Scanner input = new Scanner(System.in);for(int i=0;i<100;i++){
System.out.print("请输入数字：");int num1 = input.nextInt();if(num1==2||num1==3){
System.out.println(num1+"是质数");}else if(num1%2!=0&&(num1+1)%2==0){
System.out.println(num1+"是质数");}else{System.out.println(num1+"不是质数");