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+"
");
        }
        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+"
");
        }
        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；