shiyan9_6.java

来自「实现一个二进制bin文件的生成」· Java 代码 · 共 60 行

import java.io.*;
public class shiyan9_6 
{
	RandomAccessFile bin;
	public static void main(String args[]) throws IOException
	{
		shiyan9_6 s=new shiyan9_6();
		s.createprime(100);
	}
	public void createprime(int max) throws IOException
	{
		bin=new RandomAccessFile("F:\\123java\\primes.bin","rw");
		bin.seek(0);
		bin.writeInt(2);
		int k=3;
		while (k<=max)
		{
			if(isPrime(k))
				bin.writeInt(k);
				k=k+2; 
		}
		output(max);
		bin.close();
	}
	public boolean isPrime(int k) throws IOException
	{
		int i=0,j;
		boolean yes = true;
		try
		{
			bin.seek(0); 
			int count = (int)(bin.length()/4);
			while ((i<=count)==yes)
			{
				if (k % bin.readInt()==0)
					yes=false;
				else
					i++;
					bin.seek(i*4);
			}
		}catch(IOException e){}
		return yes;
	}
	public void output(int max) throws IOException
	{
		try
		{
			bin.seek(0); 
			System.out.println("[2---"+max+"]中有"+(bin.length()/4)+"个素数:");
			for(int i=0;i<(int)(bin.length()/4);i++)
			{
				bin.seek(i*4); 
				System.out.print(bin.readInt()+" ");
				if((i+1)%10==0)
					System.out.println();
			}
		}catch(IOException e){}
		System.out.println();
	}
}