io方面

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面试宝典目录-文章链接

1. 请写一个程序的读写，要求用两种方式一种是低层流另一种是高层流。

import java.io.FileWriter;
import java.io.InputStream;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.BufferedReader;
import java.io.FileReader;

public class Untitled1 {
    public static void writeFileChar() throws Exception {
        FileWriter f = new FileWriter("c:\\aa.txt");
        InputStream is = System.in;
        int c = is.read();
        while (((char) c) != 'x') {
            f.write(c);
            c = is.read();
        }
        f.close();
        is.close();
    }
    public static void writeFileString() throws Exception {
        FileWriter f = new FileWriter("c:\\aa.txt");
        BufferedWriter bwr=new BufferedWriter(f);
        BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
        String c = bf.readLine();
        while (!c.equals("stop")) {
            bwr.write(c+"\r\n");
            c = bf.readLine();
        }
        bwr.close();
        f.close();
        bf.close();
    }
    
    public static void readFileChar() throws Exception {
       FileReader f = new FileReader("c:\\aa.txt");
       int c = f.read();
       while (c!=-1) {
           System.out.print((char)c);
           c=f.read();
       }
       f.close();
   }
   public static void readFileString() throws Exception {
       BufferedReader bf = new BufferedReader(new FileReader("c:\\aa.txt"));
       String c = bf.readLine();
       while (c!=null) 
       {
           System.out.println(c);
           c=bf.readLine();
       }
       bf.close();
   }

    public static void main(String[] args) throws Exception {
        readFileString();
    }
}

2. 如何列出某个目录下的所有文件

引用

Import java.io.File;
File f=new File("C:\\");
        File[] f1=f.listFiles();
        for(int i=0;i<f1.length;i++)
        {
            if(f1[i].isDirectory())
            {
                System.out.println("dirctory is"+f1[i].getName());
            }
            else
            {
                System.out.println("file is"+f1[i].getName());
            }
        }
    }

   
3. 如何列出某个目录下的所有子目录

public static void main(String[] args) throws Exception 
   {
       getFile(new File("C:\\entityBean"),"\t");
   }
    public static void getFile(File f,String sem) throws Exception
    {
        System.out.println(sem+f.getName());
        File fl[]=f.listFiles();
        if(fl.length>=1)
        {
            for(int i=0;i<fl.length;i++)
            {
                if(fl[i].isDirectory())
                {
                    getFile(fl[i],sem+"\t");
                }
            }
        }
    }

   
4. 判断一个文件或目录是否存在

File f=new File("C:\\entityBean");
if(f.exists())
{
	System.out.println("exist");
}
else
{
	System.out.println("not exist");
}

面试宝典目录-文章链接