question7.java

java课程的资料以及实验的代码

class PrimePrintout
{
	//number must be greater than 1
	public static boolean isPrime(int number)//check whether number is prime, return true if prime
	{
		int i;//internal loop variable
		boolean status=true;
		loop: for (i=2;i<=(int)Math.sqrt(number);i++)
			if (number%i==0)
			{
				status=false;
				break loop;
			};
		return(status);
	}
	
	public static void main(String args[])
	{
		int length=args.length;
		if (length<2)
		{
			System.out.println("invalid number of arguments\n");
			System.exit(1);
		};
		int lowRange=Integer.parseInt(args[0]);
		int upRange=Integer.parseInt(args[1]);
		if ((lowRange>upRange)||(lowRange<=0)||(upRange<=0))
		{
			System.out.println("invalid arguments\n");
			System.exit(1);
		};
		int i;// internal loop variable
		if (lowRange==1) lowRange=2;
		for (i=lowRange;i<=upRange;i++)
		if (isPrime(i)) System.out.print(i+" ");
	}
}