java文件的I/O

【原创】

java文件的I/O操作，简单来说就是向文件中写入数据以及从文件中读出数据，这是我们平日做的最多的操作，这里给出两种文件I/O操作，当然还有许多的操作方法，各种流的使用，可谓是高深莫测；不管了，直接怼代码：

 package com.jiajia.filedemo;

 import java.io.BufferedReader;
 import java.io.BufferedWriter;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.FileReader;
 import java.io.FileWriter;
 import java.io.InputStreamReader;
 import java.io.OutputStreamWriter;

 public class Demo_1 {
         public static void main(String[] args) throws Exception{
         String filename_input = "/Users/fanjiajia/Desktop/temp";
         String filename_output = "/Users/fanjiajia/Desktop/temp2.txt";//若temp1不存在，他会自己给你创建一个
         String str = read_1(filename_input);
         System.out.println(str);
         writer_2(str, filename_output);
     }
     /**
      *文件读取方法一
      * @param filename
      * @return
      * @throws Exception
      */
     public static String read_1(String filename) throws Exception{
         File f = new File(filename);
         FileInputStream f_in = new FileInputStream(f);
         InputStreamReader isr = new InputStreamReader(f_in);
         BufferedReader buf_reader = new BufferedReader(isr);
         String s;
         StringBuilder sb = new StringBuilder();
         while((s=buf_reader.readLine())!=null){
             sb.append(s+"\n");
         }
         buf_reader.close();
         isr.close();
         f_in.close();
         return sb.toString();
     }
     /**
      * 文件读取方法二
      * @param filename
      * @return
      * @throws Exception
      */
     public static String read_2(String filename) throws Exception {
         FileReader filereader = new FileReader(filename);
         BufferedReader in = new BufferedReader(filereader);
         String s ;
         StringBuilder sb = new StringBuilder();
         while((s=in.readLine())!=null){
             sb.append(s+"\n");
         }
         in.close();
         filereader.close();
         return sb.toString();
     }

     /**
      * 文件写入方法一
      * @param str
      * @param filename
      * @throws Exception
      */
     public static void writer_1(String str,String filename    ) throws Exception{
         //将给定的字符串输出到filename文件中
         FileWriter f_writer = new FileWriter(filename);
         BufferedWriter buf_writer = new BufferedWriter(f_writer);
         buf_writer.write(str);
         buf_writer.close();
         f_writer.close();
     }
     /**
      * 文件写入方法二
      * @param str
      * @param filename
      * @throws Exception
      */
     public static void writer_2(String str,String filename) throws Exception{
         File f = new File(filename);
         FileOutputStream f_os = new FileOutputStream(f);
         OutputStreamWriter os  = new OutputStreamWriter(f_os);
         BufferedWriter buf_writer = new BufferedWriter(os);
         buf_writer.write(str);
         buf_writer.close();
         os.close();
         f_os.close();
     }
 }

很明显直接使用FileReader 和 FileWriter这两个类并结合BufferedReader／BufferedWriter很方便

其实FileWriter类的对象w直接就可以write，并且在创建是=时候，如果是new FileWriter（。。。，true）；第二个参数为true的话，便是在文件末尾写；