素数java程序找不到错误 [英] java program of prime number unable to find error

问题描述

class prime
{
public static void main(String args[])
{
System.out.println("number is :"+" "+args[0]);
 int i,n;
i=Integer.parseInt(args[0]);

for(n=2;n<=i-1;n++)
{

if(i%n==0)
{
System.out.println("number is not prime"+ " "+i);
break;
}

else if(i==n)

System.out.println("number is prime" + " "+i);
}
}
}

推荐答案

更改:
1. else if(i == n)///这在for循环内.应该在外面.

试试:

Change:
1. else if(i==n) /// this is inside for loop. Should be outside.

Try:

for(n=2;n<=i-1;n++)
{ 
  if(i%n==0)
  {
     System.out.println("number is not prime"+ " "+i);
     break;
   }
}
if(i==n)
  System.out.println("number is prime" + " "+i);

作为进一步改进(不是错误)，您可以在n/2被越过后停止循环，就好像给定数字的一半没有任何因数，而一半以上也没有.

As a further refinement (not an error), you can stop your loop once n/2 is crossed as if half of a given number does not have any factors then more than half too would not.

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