课后总结

package testw;

import java.util.Scanner;

import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.InputMismatchException;
public class test
{
	public static void main(String[] args)
	{
		long start = System.currentTimeMillis();
		
		int LENGTH=3;//数量
		int FANWEI=10;//   n  :    -n   ~   +n
		int inum;
		int j=0;
		int m=0;
		int i=0,r=0,k=0;
		
		String snum="";
		String fileName="number.txt";
		int [] num=new int[LENGTH];
		 int array[]=new int[LENGTH];
		 long maxsum=array[0];
	     long maxstart=array[0];
		
		try
		{
			File f=new File(fileName);
			if(!f.exists())
			{
				throw new Exception("文件"+fileName+"不存在");
			}
			//写入
			FileWriter fw=new FileWriter(f);
			PrintWriter pw=new PrintWriter(fw);
		//for(r=0;r<10;r++)
			//{
				for( k=0;k<LENGTH;k++,m++)
				{
					inum=(int)(1+Math.random()*FANWEI*2)-FANWEI;
					pw.print(inum+" ");
					if(m==20)
						{
							pw.print("\n");
							m=0;
						}
				}
				
			//}
		pw.flush();
			
			
			//读取
			
			FileReader fr=new FileReader(f);
			Scanner in=new Scanner(fr);
			if(!in.hasNext())
			{
				throw new Exception("文件"+fileName+"内容为空");
			}
			
			while(in.hasNext())
			{
				
				/*if(j>=LENGTH)
				
				{
					System.out.println("数字过多，多于"+LENGTH+"将不予读取");
					break;
				}*/
				 if(maxstart<0)
		            {
		                maxstart=0;
		            }
				 m=in.nextInt();
				 System.out.println(m);
		            maxstart+=m;
		            if(maxstart>=(Long.MAX_VALUE/2-1)||maxstart<=(Long.MIN_VALUE/2-1))
		            {
		            	throw new Exception("数字过大溢出");
		            }
		            if(maxstart>maxsum)
		                maxsum=maxstart;
				j++;
			}
			FileReader fr2=new FileReader(f);
			Scanner in2=new Scanner(fr2);
			while(in2.hasNext())
			{
				if(j<=1)break;
				if(maxstart<0)
	            {
	                maxstart=0;
	            }
				m=in2.nextInt();
				System.out.println(m);
	            maxstart+=m;
	            if(maxstart>=(Long.MAX_VALUE/2-1)||maxstart<=(Long.MIN_VALUE/2-1))
	            {
	            	throw new Exception("数字过大溢出");
	            }
	            if(maxstart>maxsum)
	                maxsum=maxstart;
	            j--;
			}
			
	       
	        System.out.println("max=:"+maxsum);

		}
		catch(InputMismatchException e2)
		{
			System.out.println("数字过大或输入格式不对");
		}
		catch(Exception e)
		{
			System.out.println("错误于：\t"+i);
			System.out.println("错误！！！");
			System.out.println(e.getMessage());
			e.printStackTrace();
		}
		
		
				long end = System.currentTimeMillis();
				//System.out.println("程序运行时间："+(end-start)+"ms");
		
	}
}